This old issue of Dragon 124 might help a bit with your question. It was a resource back in the day, though it's not 5e. You asked for any resources including those using old editions--and that article is a treasure trove of useful info you can use.
One particular bit on page 57 of the issue:
As to their digestive fluids these are produced and held in movable,
elastic cavities or bubbles within an athcoids body. When prey is
engulfed by a cube, one or more of these mobile bubbles are shifted
into contact with the prey. Such fluid has no effect on metal of any
sort, and, as we have all heard, metal objects are held for a time
within the creature, then expelled through its skin; but the fluid has
devastating effects on flesh and cellulose.
I would posit, based on this that the cavities or bubbles are maintained within the creature, and that upon death, they deflate and the creature loses cohesion.
It's DM call on if the acid of the cube still has an effect after it's "killed." What I have done, as it loses hit points is allow it to puddle in the hall around the PCs. For about a round it remains acidic--but that's a DM call there. As they take away the hit points from the creature, it does naturally move toward warmth vibration and sound, so even if it is a bit shorter, it will try to block their way.
Once it's dead, all that mass has to go somewhere, and I work it like a gel-filled balloon that's been popped. But--you can work it the way you did, ruling that it maintains cohesion for up to an hour after death or more, or less, that's your call as the DM.
I have also had some fun with PCs once they have defeated the creature by having the gel start to coalesce again--remaining bits into baby cubes. The PCs were so freaked out by it shifting to come together again that they simply ran away, despite the fact that the baby cubes would have moved away from them as they are now too big to eat. That isn't at all canon--I just like throwing something their way they haven't seen.
Not all cubes are going to be the same--I use the MM as a jumping off point and assume that some creatures in an isolated dungeon might have developed slightly differently. It also keeps my players from metagaming too much--if they are of a particular level, they expect specific creatures in their range, which is annoying, because they will try to use out of game knowledge to fight said creatures.