your goal isnt just to double up necessarily when just the blinds and antes can increase your stack by 20%+ without actually risking your tournament, think about that. sometimes a 3/7 off in the sb is worth the all in with 4-6 bbs once antes kick in. it just varies, but you want fold equity (enough chips to shove and not give marginal hands that know they are worse the odds to call anyways). folding to 3 bbs is dangerous you'll almost always have to draw cards for your tournament life