Brake Masters BM sold me "lifetime warranty", then refused to honor it Kingman Arizona

On March 25, 2006 I had my pickup worked on in the shop. They worked on both the front and rear brakes to the tune of over $700. At the time, the sign painted on the shop window advertised a 'lifetime warranty' on the brakes. Nothing was said about the size of the truck. On March 21, 2007 I had some problems with the brakes. Again I had them worked on, with another $187 bill. On this invoice was written that no warranty would be honored as this was a 3/4 ton pickup. Should not the time to let me know about this be before I purchased the original work? Is it reasonable or fair to limit warranties one year after the purchase?

Despite contacting them 3 different times for help with this, they have refused to answer me.

Mike
Kingman, Arizona
U.S.A.