For those who haven't done anything with the black books - please don't read any further...

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Having said that, I want to ask people if they discovered if the Apocrypha zones ever respawn?

While they are interesting, I'm rather hoping they don't. You see, I'm kinda wanting to use the Vessel found next to the knowledge book in "The Hidden Twilight" as a portable emergency storage container that I can carry wherever I go. I was also thinking about decorating the nearby altar - just to make it my own private portable partitioned place of perpetuity!

Any word on this would be greatly appreciated! Thanks!

Put this in spoiler section...

As for your question...no. I've never had mine respawn and could continually go back to it.

They've respawned for me (at least one anyway). I've been using the black book "The Sallow Regent" and the first time I revisited, the black soul gems at the end had respawned, as well for the boss chest.
I'm not quite sure how long it would take, but I know that at least THAT one respawns.
Hope this helped.

Bear in mind you can't use a black book off of solstheim. so it's only partly portable