blind stealing

[umdpoker]

how important is blind stealing at 1/2? i almost never steal, just because i know it has to increase variance. by this, i mean that i won't raise garbage in lp to try to get the blinds. i do, however, lower my standards for raising just because the odds of kto/etc being the best hand have just skyrocketed. so, how much of your profits do you think come from blind-stealing? i often see people defend their blinds til death, even with absolute crap, so does it really make much sense to steal in these games? i am about to move up to 2/4, where i amy need to learn this skill(heads-up play). what level do you think blind-stealing and blind-defense becomes necessary in order to survive?