I've been wondering this for a while actually. When do i know a chains simply had too much and needs to be replaced?

I've heard something about when kinds occur at too many points but is there more to it? As far as stretching too much i still have about maybe 2 or 3 inches of travel on the "adjuster nuts" for the chain. Would i just keep tightenting till the nut as at the end of its possible travel??

Please enlighten me:)

either till the chain can't be adjusted any further, or if the sprockets are worn then you need to replace the chain with the sprockets.

I can't remember the exact numbers but the basic method is to measure the length of a set number of links.

Say 21 links ought to be 18 inches long in a new chain.
If any section of your chain has 21 links that have stretched to be over 19 inches for 21 links then the chain is shot.

The haynes manual has then number of links to measure over and the
limits to how long this can get.
I'm sure some nice person with a haynes to hand could post the details.

In my experience with o-ring chains, they go through most of their useful life requiring very infrequent adjustment.  When they get to the point where you need to adjust them every few hundred miles, they 1) aren't going to last much longer, and 2) you might as well replace them before they trash the sprockets as well.  The amount of mileage you get between "starting to stretch quickly" and "fused hunk of scrap metal" isn't worth trying to extend the life of the chain in my opinion.

Check out this topic.