Battery failure will happen with every electronic lock. Most of these locks have the batteries on the outside beneath the key pad, and they are easy to replace. I can't tell you how many "my safe won't open" calls that we get where fresh batteries do the trick.
Aside from batteries, the most common failures we see are in the lock body themselves. This can be a mechanical function, or part of the electronics. Each manufacturer has it's own failures that it's known for, it is not common between makers.
When the lock fails, it's usually when the door is closed and locked. As a result, most of these situations require drilling the safe.
Keypad failures make up the least amount of calls that I get. It does happen, but it's easy to fix. You can either replace the keypad, or splice in a temporary to open the lock.