There is a big problem with the new prison mines, they're just don't renew often enough so it often happens that they get completely mined out. Even when I mine in B mines on my own I almost mine out the whole thing so with two or three players there's nothing left to mine very quickly. I hope someone can make them renew faster, thanks.
This was a problem for me too. With an effv pickaxe and superbreaker you can easily mine out an entire mine by yourself (which happened all the time) then you are left waiting another ten or so min not being able to make any money. Better MRL schedules or larger mines (easiest to change MRL refresh rate than build bigger mines) would easily solve this problem.
Or they could also implement a feature that resets the mines again when you mined the whole thing out on top of the current reset schedule cause it can be kinda annoying if the mines reset too often.
That could be a possibility but in B mine it is not worth it to mine the soul sand our glowstone so then the mine would not reset because I'm not wasting time mining things that sell for almost nothing.. I'm not saying change the MRL schedules to two minutes lol.