Trying to gather info here. I progressed mostly fine through the mines, and the stamina drain was not great, but I could reasonably expect to get at least to the next elevator stop with about half a day's mining. Getting from 30 to 35 and 35 to 40 was a nightmare and took me what felt like an eternity, and far too many stamina refill items.
I'm pretty sure that the problem has to do with the sheer number of rocks in the far levels, but even accounting for that it felt specifically excessive. I feel like there might be something up with the balance there, but if this is just bad luck on my part, I'm not gonna clutter feedback even more. I've already said I think the chance for holes down should be higher