Wow, Dan's advise sounds like the final word.
PS: If you are a bicycle thief, please do not read the next two paragraphs.
If you ever lose a key or combination and have to cut through a lock, I suggest getting a hand-drill mounted cutting wheel at the hardware store and the jig onto which it mounts.
If you have a battery operated hand drill, all the better. These cutting wheels go through any lock I have ever seen and it takes less than two minutes for the toughest lock.