Cylinder head cover gaskets - how long should they last - where to get new?

I goop my end plugs with Permatex number 2, the black sticky stuff. The silicone sealants seem to leak easier. On the gasket, I goop it to the head with number 2 then put copper sealant on the top half. It releases easily when time to remove the cover.....I also use copper sealant on the bolts that go through the end plugs too. Oil will weep down the threads and drip out, flow back on the fins and fly off onto your pants leg......chris3