Like the answers to many other questions, the answer to this is - it depends. There are several factors that can determine how long a 22 barrel will last including " what is your definition of last". Is it "when will it start to lose it's accuracy" or " when will accuracy decline to a point that the barrel is completely unusable."
Quick answer: I know of 22 barrels that have lasted 200,000 plus rounds and are still being shot with very good accuracy and I know of 22 barrels that appear to have been shot out (complete loss of accuracy) after 5,000 rounds. There appears to be a direct correlation between longevity of a barrel and the care given to it
Big bore rifles typically see a much faster curve for reaching the end of their useful lives. This is because of tremendous high temperatures traveling down the barrel along with high pressures. I have heard some say that a big bore barrel is expected to get around 3000 to 5000 rounds before becoming useless. Some say it's even less with large cartridge, hotter powder, smaller bullet calibers like 22-250. Just another plus for shooting our little tack driver rimfires.
My advice to all is to not worry about shooting your barrel out. Relax and shoot your guns as you intended when you bought it. Know that I have only seen two barrels in my over 30 years that could fit the description of being shot out and both of these barrels died at an early age from pure neglect of proper maintenance and care.
It is important though that you give your rifle barrels the proper care and at the right times. Below we will get into how to do that.
Keep your barrel cleaned and oiled when not in use
At least one, maybe both, of the barrels I have seen start to malfunction at an early age suffered from idiotic cleaning techniques. I usually don't refer to anything shooters as idiotic except in the these cases.
The owner of one of these barrels was too cheap or didn't want to go out and find a good cleaning rod for his new 17 hmr. The smallest rod he had was for a 22 and of course it wouldn't work with the 17 caliber barrel.
So he just used what he had, a metal clothes hanger. Now even this would take some time to destroy the crown end of the bore but his metal coat hanger was special. It still had the little curly end on it that bound the hanger together and that end is what was pushed the path out of the muzzle.
In addition, it wasn't straight and very flexible so the inside of the bore was taking constant abuse. There is no telling what the muzzle on this rifle went through as he pulled it back through the barrel.
The second rifle had a similar life but was also left outside in the elements for months. Apparently this guy's wife wouldn't allow a firearm in the house. It sat outside in the carport, not a garage with walls, for months and was literally never cleaned or oiled.
The the owner wondered why it wouldn't hold a group when he decided to bring it to the range. The crowned muzzle end of the rifle was rusted so bad (we live in a humid place) it had gone much further than just being surface rust, the metal had begun to pit.
His shots at 50 yards were at least within a 6 inch group. No kidding. Now some of this could have been because this guy couldn't shoot, but nobody is that bad. Some of this was the rifle.
I didn't even bother to shoot it myself, I just advised him to throw the rifle away and wait until he his family situation was under control so he could keep his firearms in the house before he purchased another one.
Guys if you are going to buy a rifle, have a place to store it where the humidity is normal. A gun safe inside a normal home is more than adequate. The last thing any of us wants is to have one of our family hurt with a firearm that we keep inside our house. Owning guns just means that you must be responsible enough to make them safe and properly care for them. Pictured right is a very affordable 4 rifle safe. Click the image if you want to check it out on Amazon.
Clean your rimfire barrel once every 300 - 400 rounds. Use a good rod. Hoppe's solvent works great. Pass a patch wet with solve through the bore once. Then pass a brass brush through the barrel twice. The use clean pouches until they come out clean. Very simple, yet very effective. Using this technique will allow your barrel to live a long an healthy life.
Don't shoot with your barrel hot
The cold shot theory suggests that every shooter should have a mulligan on his first shot. This is because the barrel is cold and is not at the temperature where successive more accurate, tigher grouping shots will be fired. Therefore an outlier or flyer is excused on this cold bore shot.
The fact is the barrel is constantly changing temperature. Every shot sends a 4000 degree flash of fire down the barrel. From one shot to the next the barrel is constantly heating and cooling if enough time is given between shots. The hotter the barrel, the faster your barrel will wear.
I don't mean to say that you should never fire back to back shots. Taking a string of back to back shots infrequently is not a big issue. But I can say that for optimum accuracy and minimized barrel wear, let your rifle cool as close to ambient temperature as possible in between shots to maximize barrel life.
This is hard to do at the range when the reason you came to the range is to shoot. Bringing another rifle to alternate with might be worth the effort and eliminate the periods of boredom.
Keep the rifle in the shade at all times if possible. A hot sun on a hot summer day can really slow the cooling process. Experienced shooters may even use a wet towel over the barrel in between shots.
In between shots keep the bolt open and the muzzle up. This has a chimney effect allowing hot air to escape the muzzle while cooer air enters the chamber end of the barrel. Some bench rest competitors actually circulate water through the barrel in between rounds. It works but can be pretty messy and not really worth the effort unless you are competing for one hundredth of an inch.
My favorite way to force cool a barrel is with air. There are devices made that have a tube that fits right into the open chamber of a rifle that is attached to a small fan motor. This forces air through the barrel and really speeds up the rate of cooling. The reduction in cooling time is well over 50%. This unit is battery operated and doesn't require an outlet.
Use a stainless steel barrel
Stainless barrels will last longer than a conventional barrel. Research indicates you can expect to increase barrel life around 20% over the standard. Take a look at the price of the barrel vs this 20% expected longer service to determine what the best route to take would be.
Coated bullets are becoming a potential
There are many coatings now being used on bullets that will supposedly accomplish several things when fired through a rifle including extending barrel life My research has not shown data that proves this fact and there also some known drawbacks to some of the coatings used. I will reserve any comments on this option until more information is available.
Everything I know about how to make your rimfire barrel last longer is mentioned in the material above. This information is just presented as knowledge to allow you to have a normal barrel life. By doing these things you should be able to pass an accurate rifle down to your kids.
Don't however become so obsessed with extending barrel life that you don't enjoy your rifle. Enjoyment is why you bought it. It is a tool for a specific job - in our case, long range rimfire shooting. Use it and enjoy.