RTV, Permatex, Aviation Form-A-Gasket, The right stuff etc....

Not a valve cover I wouldn't put RTV on a valve cover... But yes at one point or another I've taken all the tin off of my engine... And of course the point you're making is it doesn't come off easy. And it didn't. But I'm not the kind of guy who sticks in a drag strip only Cam and expecting great Street manners out of it... There's always a trade-off.. I'll pay the extra 10 $15 a tube and the extra labor to get the parts off when or if they eventually come off.
I repeat, did I say I don't like leaks...
Using standard gasket sets, RTV and Permatex High Tack adhesive I have build many motors with out leaks. And they will come apart with out major issues. The keys to leak free engine building are: clean - flat mating surfaces, quality - defect free gaskets, correct torque on fasteners, and knowing where and what kind of sealant - adhesive to apply.