Fred,
Is that the mileage on your tires? 18,000 or did you mean to say 1,800?
If you go to this website, it will give you some generalized information on ST tires, how to maintain them and what to expect from them.
The general rule seems to be 3-5 years and 5,000 to 12,000 miles of life.
If you've got 18,000 miles on yours, you've been "living on borrowed tires" for quite some time..... That might explain your blowout last year and could predict your future tire problems.
Here's that website:
http://www.americastire.com/dtcs/inf...rTireFacts.dos