18 years on TTIs, and about 120,000 miles including 5 winters. But to be fair, the winters were hard on the topside welds on the merges. I had to repair them twice in the first 8 years or so, and the drivers side needs patching again. The head flanges never leaked or loosen off by themselves, or burned the gaskets out... on the Eddies.I replaced the first set of gaskets after about wearing them out with 10 engine swaps. I still have them and they are my back-ups. The second set are about 13/14 years old .