My motto:
If you like it, buy 1 yard
If you love it, buy 3 yards
If you can't live without it, buy 5 yards
but only if on sale!! I also buy the scrap packs at the LQS, and remnants from on-line fabric sites.
If I am close to finishing a bolt, I always take it all.
I have already identified the lucky recipient of my stash in my will....If I ever start to feel guilty about the quantity, I take the oldest (and not my favorites) and give it away to the guild to make charity quilts....eases my conscience...