you don't HAVE TO even remove the lids, I do it to kinda give it a boost.
A lot of my pre-mixed juices I just set, with lids on, out for a week, unless they taste whack or don't have enough flavor then i do the 24 hour lids off deal.
It doesn't make a HUGE difference if it's one or both caps, if you're doing it for 24 hours. the only difference is ur juice will darken faster. You could even just shake it, pop the caps off, put them back on and let them set.
I leave my DIYs off ALWAYS for the 1st 24, but it just depends with the pre-mixes.
hope I helped!