Like you when I reinstalled the valve cover after my first valve adjustment I used RTV on the half moons. On my second adjustment I didn't separate the seal from the cover at the half moon, just let the RTV hold it together and used the seal again. 9k miles and no leaks. Those seals are pretty hearty if you don'r abuse them.
2009 Wee Strom ABS (current)
1987 Harley FXR Low Rider Sport (current - with 206K miles)
2009 Aprilia Mana 850, 2006 SV650, 1984 Yamaha Virago 1000 (all sold)
Silver Strom Club Member #11
Wee Farkles: Russell Day Long Seat, Madstad with Moose Adventure Shield +4'', SWMotech Centerstand, 1'' up & back bar risers, Givi XS308 Tankbag, Aprilia mirrors, Framesliders, Fenda Extenda, Elka Shock.