Motorcycle Tires: To Change or Not To Change

Double D Cycles is in a few motorcycle forums and a question came up from one of the members:

"How worn do you let your tires get? My wear bars are showing, but the tire still looks like it has plenty of tread. Hate to change tires if they still have 1,000 miles on them....."

Checking tire tread

Waiting way too long

The comments ranged everywhere from the idiotic comment of "I wear mine down to nothing. I love to slip and slide!" to my short and sweet comment of "The wear bars are there for a reason. Why risk it?" 

How do you decide when or how often to change the tires on your cycle?