Holey Flap! my bike eats shock covers fast

check out http://www.gearingcommander.com/

it'll tell you EVERYTHING you need to know about teeth wear, chain length, wheelbase, speed, rpm, gear shifting, stretch, and geometry. you'll be able to change virtual sprockets or chain lengths to see each effect.

We generally center axle in adjuster with the marks then get the chain as close in length to that. A good quality chain will stretch but should not stretch enough to be longer than what you have left on the adjuster. After the first few good rides you should be about done adjusting your chain, maybe minor tightening adjustments after that. I have a real problem adjusting my chains I always over tighten them then have to go back n loosen them up lol.