I have never torn a bike down that early. I think it depends on how hard you are running the bike. If you are racing and running it close to lean, you would probably need to replace the top end regularily. On the other hand, if you are trail riding in the middle of the RPM range and the bike is jetted right, you could go for several months. I would change the oil after each ride for the first two or three rides since there may be metal shavings due to break-in.
What you really need to do is grease the swing arm bearings, the rear shock bearings (all 4 sets) and the steering head bearings. My 03 KDX 200 had NO grease in the rear shock bearings and almost no grease on the swing arm bearings and the steering head bearings.
Congratulations on the new bike-
JCW