Thieves guild lock box reset

What is the reset timer of the practice lock boxes in the thieves guild?

There are 5 lock boxes in the thieves guild with all the different difficulties for opening them. There is also a note in the middle of the chests that says:

"These chests are for practice use only. Please Refrain from using them for storage. The locks on these chests have been specially constructed to reset themselves after a short amount of time. If you have any issues, please speak to Niruin."

I talked with Niruin and he didn't have anything to say about reseting the chests.

I opened all of them then did about 10 different jobs for Delvin and Vex going from Riften to Markarth, Solitude, etc. I know I have been gone at least 10 game days and they are still not reset.

Any idea what the reset timer is?

I read that they reset after 10 days of not visiting the cistern.

I haven't tried it yet, but its worth a shot: it's also the same time frame that many ores reset.