If you are in the mining guild, after drinking a dwarven stout, and the stout power runs out which makes your mining go down to its original lvl, does it keep you in there till you drink another?

You get to stay in there, even if your mining level goes back down. It's not going to kick you out. ;)

And after you're done mining, you can walk out (or climb out) without a problem.

Yeah, it can run out quickly so I suggest you drink it just before you climb down the ladder, and then drop the glass. After your mining goes abck to 59, you will still be able to mine there. And when you put your coal back into the bank, just drink another one and repeat until you get 60 mining.

Thanks guys. Unless other people need this information, it can be locked.