if they keep stretching, give more... the visible sign you've gone too far is if no node spacing develops... when extreme the leaves push each other upward when all originating from a tight length of stem. it's going to be tight the first 2-4 days, but should show 'some' spacing as nodes stack up.
my seedlings usually need ~full power within 24 hours... numerous times i've tried to not do it, but end up with stretchy plants, lol. So, fuck what 'they' say when the reality doesn't match. What matters most is how the plant directly in front of you is behaving. React to that, and it'll be fine. Some may be ready before others.. .again, node spacing is the guide.