You don't mention which bike this is happening with, but assuming it's one of the T3 1200s it may be very simple....
First, *do not* overtighten the cam cover bolts! Tighten them as spec'ed and in order; they bolt directly into the head!
Second, one thing a lot of people miss is that the gasket in question is spec'ed to have RTV put on it in order to seal properly at the 2 half-moon cutouts on each side. I'd be willing to bet that that's where your problem is; that gasket is usually good for well over 50,000 miles.
Also, there is a maintenance schedule. It shouldn't take a cheating spouse to get you to look at your cam cover!
Cheers,
-Kit