56 is incredible! That isn't just a "humble" record. I don't know if their is a limit, but I wouldn't recommend spending too long on it. My current record is under 56, but I've never taken multiple days (or even sittings really) for one survival attempt. In fact, most times I play survival, I'll only spend an hour or a few on it.
If you goal is overall improvement (and not necessarily your "personal best" highest survival score), then I recommend not taking any longer than an hour per puzzle; in fact, even 30 minutes is a lot and I seldom take longer than this for a puzzle.
Here is a similar video I made which might be useful for you:
I have been working on several puzzles for 3-4 days because I don't have much time, and the puzzle has not been reset. Do you know if there is a time limit of 7 days or more before it restarts? My record is a very humble 56.