The Tires Dilemma

When exactly do you change the tires? With 10,000 miles on my tires and what appears to be a lot of good tread left, I opted to have new tires put on. I attempted to do my research and enlist the advice of many veteran riders who all had different opinions. Some say it depends on the type of tire, the type of riding and on and on. There doesn't seem to be any definitive answers. Unlike car tires that you ride on until the tread is worn, I didn't want to take that chance. Riding on just two wheels is risky in and of itself. I keep hearing about car tires on the rear? If anyone out there has some advice,,,,,,,,,,,,,,,,,please share!!