Depends on the safe, tools and person. I watched a lock smith open a Liberty safe, he called liberty to obtain the correct drill spot, to not hit the double lock, and it still took him 4 hours. He didn't know what he was doing, masonry bits in a hand drill. With my mag drill and a carbide single flute drill it would have been a 5 min job.
A friend of mine buys and sells safes, he simply cuts a hole in the back to remove the lock cover from the inside so he can tell a buddy turning the dial what way to go and how much. Once open he welds the back back in place.
Those crappy sheet metal safes are to keep them out of childrens hands, they could get to them too with a screw driver but Dad would find out once he got home.