3 years on mine.I changed springs,retainers.and keepers because I run .588 solid 4 speed.Used the Felpro marine gaskets.My machinist back cut the valves and lapped them a bit.He also opened them up some.I run 3/8 alloy push rods and they just clear.The overhang has been fixed.The marine gaskets fit fine with my heads as did the 19 gaskets.Mine is street/strip and gets beat on quite a bit.Rocky