I never really thought about putting a lock on our fifth wheel until this year when I started seeing a lot of stories about stolen RV's. How long have you been locking your king pin?
My Wife's thought on the lock is "you have a huge investment in the camper The cost of the lock is negligible in comparison to the loss if the camper was stolen". We lock ours now. I did see 2 others locked this weekend at the campground.