What Diamond has stated as far as maintenance goes is really all there is to it. I bought a 2007 8-Ball back in August 2007 and although I don't ride nearly the amount you do, the bike has been nothing less than great. Basic maintenance has been kept up and there have been no problems at all over the 28,000 miles I've ridden. It's a terrific bike I highly recommend to anyone.
2012 Cross Country Tour
Stage 1 with RPW Slip-on Mufflers
2" Pullback Bars
Ness "Rad" Mirrors