I've been riding a 1999 Carbon Mono frame since late 2001(when I finally built it up w/Campy Record/chorus 9-speed) , and have over 24K miles on her. I'm not gonna say which frame builder it is, to put a certain emphisis on them (hint: its a French frame builder). The frameset was in the $1800-2000 msrp range. I just recently replaced the front fork(oem = 1" straight blade carbon leg/ Cro-mo steerer- threaded) , with the same builder FULL Mono - Carbon fork/ straight blade, and was able to lighten up the front end by about 1/2 pound !
I plan on riding her probably another 3-5 more years(should be 30-35K miles by then) , then possibly look into selling her for something.
JUst take care of your rig.. and it will take care of you! I do my best while riding to pick the SMOOTHEST line, trying to avoid any uneven surfaces ahead of me.