Re: Brass Life
Already pretty well described here by previous posters, but this really is an open-ended question. I've seen plenty of brass that was rendered into scrap metal after the first firing, simply because it was loaded too hot. Others used with relatively mild loadings, I've seen destroyed pretty quickly by improper die set up, or working the brass excessively (always a bad thing). In some other instances, the brass is worn out quickly, even when proper resizing techniques are used, just due to what they were fired in. The M1s and M14s (M1As) are terribly hard on brass, and it should be discarded after the third firing. Bolt guns, much better. Bottom line is, it varies.
Brass quality is an entirely separate issue, an it varies widely between different makes. It can also vary widely in some brands from lot to lot, just to complicate the matter a bit further.
Some issues that you do have control over, can determine just how long your brass will run. Some of these are;
1) Avoid excessive sizing wherever possible. Proper die adjustment will go a long way towards long brass life.
2) Avoid high pressure loads. Speed costs money, no two ways about it. You don't want to spend the extra money on worn out brass, slow the loads down a tad.
3) Under the heading of excessive sizing, make sure the neck dimensions of the die, and the expander ball (if you MUST use one) are the minimal specs capable of doing the job. This dimension can vary from task to task, which is one reason I think the Redding, or other similar bushing dies are about the neatest invention since well before sliced bread. Use 'em, you won't regret it!
4) Keep your brass segregated by lot, and isolated for one rifle only, even if you have others in the same caliber. One batch for one .308, and another sperate batch for the other .308, etc..
5) USE A CARTRIDGE CASE GAUGE! Wilson, Dillion and a host of others make very inexpensive gages that can help you control headspace issues. Redding makes a suoperb unit that allows this, and several other case/cartridge/bullet measurments as well. They're your friend; use them religiously.
Plenty of others here that I'm sure other folks can add to the list, but you get the idea here. Hope it helps!