If you change the fluids regularly and make sure you do not redline right after being started I think that you can easly see 100K plus on this bike. I have personally talked to someone who at the time had 87K on thier F2 and now has over 100K. My F4 has 25k right now and is still running very strong. Honda builds very durable engines in thier bikes and the F4 is no exception.
The one minor problem area you need to be aware of specific to the 600 engines is the cam chain tensioner or CCT. It is supposed to be automatic and takes up slack in the cam chain as it ages, but almost all owners of F2-F3 bikes need to replace them if they keep the bike long enough. The ones in the F4s also go bad but not quite as often. CCTs donĀ“t actually fail they just slowly stop taking up the slack in the cam chain and the chain makes a noise like loose marbles in the engine when first started. Replacing the CCT is not a huge job and easer then a cluch replacement. Many owners go for aftermarket Manual CCTs that can last much longer and can be adjusted by the user perodically.