mice are rarely a problem, especially younger ones. old haggard mice may be more of a problem, and rats are the worst.
I think the problem is, the trade, particularly the recent trend to recipe keeping, has toooooo many rules and most of which are WRONG and stupid. Hmmmmmmm that's a little harsh, but its true. If you make a list of what harms captive snakes, leaving feeder mice in the cage will be somewhere in the 85 to 100 range. The first twenty reasons are based on folks not knowing anything about husbandry. And the next bunch of reasons are, making mistakes, leave the cage open, drop something on the snake, Cutting its head off in the door(seen it) etc etc.
When a problem has occurred, its when someone feeds a healthy large mouse to a nearly dead snake that has no physical ability and could not digest it anyway. Rats, that's another story all together.