I've had the same issue, and the lock has barely been used. Bike sleeps inside at home and has it's own locker at work. The lock has probably been in the elements a grand total of 7 times. None for very long and probably half on sunny days. The rest of the time the lock is inside of the house. Oh and when the lock is taken, it's put in a pannier bag.

While lube probably will help the situation, this doesn't appear to me to be a user problem/poor treatment of the lock.