All good thoughts in this thread. Only thing I would add is that it depends on the experience of the lifter, too.
If you've always hooked and your thumbs are already mashed into submission, then you can do as you will.
But, if you are new to it, you need to mash your thumbs as often as possible to get yourself ready for that ultimate phase.
It's not like alternate grip on deadlifts where you are correcting the spin on the bar with your hands and have to do it or your can't hold it at all. Your hands are fine either way. You either hold it or you don't.
But, if you wait until your lifts get heavy to hook, then your thumbs will suffer exponentially worse because you waited until the bar got heavy to mash them. They never got to build themselves up to the abuse they will take.
You wouldn't suddenly deadlift 300 with no warmup because your back would rebel, so why would you do that to your thumbs?
Practice makes perfect. You have to practice every part of an olympic lift exactly as it occurs in order to progress at an olympic lift. You can't just say I will start hooking when shit gets heavy.
I am Anton Zdravko Martin!
Best meet lifts: Sq 150 Kg (330 lb), Bench 120 Kg (264), DL 160 (352) @89 Kg (197)
Best gym lifts: Sq 375, Bench 280 (pause), DL 385 @205 or less
Goals beyond my wildest dreams, 600 Kg raw total, 200/160/240
Hack away at anything which isn't essential. Do what you love, and do it often. Fazc.
Everything competes for recovery so more assistance is not always the best idea. miked96