The headgaskets in my 367 are on their third install, as is the pan. The intake is on it's second install, and the header gaskets are circa 1999, have been on and off about 9 or 10 times at least.The VC gaskets are reusable type and are also circa 1999, but have only been off a few times;go figure. The timing cover I think was new in 2004ish, the previous one having been worn out. I think I have saved enough on gaskets alone, to rebuild my heads one day.
The gaskets in my 4-speed are also circa 1999, and have been through more installs than I can remember.
All the many, many, rearend swaps I have done on this car since 1999, I think I might still be on the second, or maybe third gasket.
Most gaskets, I have found, don't usually wear out.
They get torn during teardown, or are over-tightened during the install, or the parts don't fit very well to start with, Or somebody used a powerful glue that just won't let go, and in some cases they get baked hard and become brittle.
There is just no substitute for good gaskets.
So what's my secret? I can't say, just lucky I guess.......
But I have to admit, changing out a slanty gasket is not my favorite thing to do.