How often should they be replaced? I put about....200 miles a week on my bike give or take. I am hearing a noise when I am up in the 80mph range or so, but when I let off the gas it goes away. My oil lvl is fine...so I am thinking tranny or hub bearings are about to take a **** on me. Anyone had a problem like this before?

 

How many miles on your bike? Wot sort of noise? Do you use a torque wrench on the axle nut (can be overtightned = premature wear) Is your wheel alignment adjustment right? Plus it may not be your bearings making the noise, brake pads, disc run out etc.
Try rotating the wheel on the stand, see if it makes any noise then, bearing noise is kinda like a "Clack, Clack" sound. Disc & pads is a scraping noise.

 

Yeah if it's the bearings, you'll know it when you spin the wheel by hand. It will bind and sound nasty. Will not spin freely.

 

its almost like a howling noise? my bike doesn't have a speedo so I couldn't tell you the mileage. Its an F3 with an F2 'race motor' according to the buy I bought it from. The tach says 10,xxx and the guy told me there was about 8,000 miles on the motor. I have had it for about 4 months, and put around 3k on it. This sounds stupid but I never heard it before I chopped my exhaust. I had a sudco complete system and shortend the canister a little. Maybe its normal? because when I let off it goes away...but if I sit in neutral and rev the motor I don't hear it. Thats kinda what makes me think its tranny related...would clutch disks going out make any noise? or just slip?