Whenever I decide to go all the way up to a Dilithium Farm for soul eggs before prestiging, I know I can get over 30,000 soul eggs from the prestige itself, but I usually try to queue up 2 boxes and a video as well, in hopes that I can immediately use those to gain another 10,000 to 25,000 soul eggs for each one of those that contains bocks.
Unfortunately, sometimes (like just now) it is an epic failure. Either (1) the videos have golden eggs and the boxes disappear upon prestiging so they can't be opened on the new farm or (2) the boxes and video both remain but all have golden eggs.
Rarely, I think the video may disappear upon prestige as well, but it's much more common for boxes to disappear.
I have found that when I prestige with 2 boxes and a video and they all remain, I can always open one box and then prestige again and the other box and video will still be there. One time I got lucky and all 3 of these things had bocks in them, which meant something like an extra 45,000 soul eggs overall beyond the original amount from prestiging.
These post-prestige bonuses are also nice for gathering golden eggs into my piggy bank, as they make it easy to spam research on a basic egg farm and a graviton egg farm I can buy thereafter. However, I've had bad experiences of the game crashing when I scroll through menus buying stuff and so I never try buying anything until I have opened both boxes and the video (or they have otherwise disappeared from me).
The point of this forum thread is two-fold.
(1) To let anyone who does not yet know that they should put this extra effort into their late prestiges so that they get more soul eggs for their time.
(2) To ask if anyone ever figured out a way to determine in advance whether or not boxes/videos will survive a prestige (or egg upgrade, for that matter) or a way to determine if they have bocks or golden eggs. Any kind of clue to this mystery would help us optimize play. Recall that the reason I believe there may be some logic beyond just randomness that decides if boxes remain upon prestiging is the fact that if I prestige with 2 boxes that stay and then open one of them and prestige again the other box (and video) will always survive that 2nd prestige.