Re: Really annoying sound.
The safest answer would be as little as possible!
If it is the wheel bearings, you can imagine what would happen if the component were to fail.
The noise associated with a failed wheel bearing progressively gets worse. If it is a very slight hum, I would say you have some time. If you can feel any play in the wheels when it is jacked up, or the noise sounds really bad, I would tackle it straight away.
Safest thing is to get it taken care of, but they usually give fair warning before catastrophic failure.