Oh man, don't spell my name with a capitol "L", I just don't deserve that kind of respect!

Barrel life, yea its fairly simple. It depends on the wear that your firearm has had over the years. Hot loads or heavy bullets will cause more wear, but heck-o-darn, if they work, they work!
Remember, most hunters don't shoot that many rounds during thier lifespans, others DO. And many rifles come with what I like to call "Factory Throat Erosion", otherwise known as "Freebore".
Freebore is a sneeky way for Lawyers and Gunmakers to keep us safe, and squeeze out a bit more velocity. Velocity sells, but freebore ain't much good for ACCURACY.
You see, all it has to do with is the distance between the bullet and the lands, the lands being the START of the rifleing in the barrel of your firearm (actually, the Lands are the "High" spots of the rifleing, all the way down the tube). If there is a "Jump", that jump is refurred to as freebore, and some say it can induce a "wobble" on your bullet just before it sqeezes into the lands, causing an "inaccuracy", something to do with harmonics, but thats another thread! As stated above by another poster, Arrowflinger I think, flat-based bullets can help with the problem, 'cause flat-based bullets are more forgiving when it comes to freebore.
Everybody knows Weatherby Rifles are famous for the amount of freebore they have, but heres a kicker for 'ya, ALL THEM DANG 'OL FACTORY RIFLES HAVE IT, at least that is my experience.
Why all this talk about freebore? Well see, you are making your own freebore when you shoot your rifle repeatedly. Your wearing it out, just like you wear your tires out on your car when you drive it.
You break hard, or "squeal 'em", you wear your tires out more, just like if you fire hot loads, or your firearm is just plain 'ol "Hot", like most magnums.
Theres an argument about repeated shooting (like match shooting) causing more damage 'cause they get that bore "hotter", but most match shooters will argue this point, I'm not comenting.
The fact is, most will claim that it IS INDEED the hot gasses produced by the burning powder (the same gases that cause the bullet to "go") that cause this same erosion, not the bullet, nor the heat, although they can't help the condition, hehehe.
Confused yet?
Well if not, you most likely get it, and its a simple math problem.
For example, something that shoots like the 6.5-284 will have top accuracy till it has around 1200 rounds, then it drops. The 308 has been known to last to 10,000 rounds (most likely around 6-8000).
The .260, if a good barrel is used has been know to make it to 3000 rounds.
Now we are talking optimum accuracy, like match shooting. Hunting accuracy will last a lot longer.
Now I figure you can base what-ever rifle you have around those three, and get a good idea on how long she'll last.
Another good idea, don't throw that 'ol rifle out just 'cause you think she's wore, REBARREL HER! You'll end up with a better-than-factory gun, that will most likely shoot the doors off of anything off the shelf, and still have the memories with what you've done with it!
GOOD SHOOTING!