I have a system that is getting up there agewise - Onkyo receiver and Bose acoustimass speakers (5.1 surround system) and subwoofer all approaching the 8 years old mark. I know the right answer might be to get new everything, and I will but probably can't do everything just yet.

To address an immediate problem, I was wondering if it is more due to the receiver then anything else. Basically, I lose audio from time to time on different speakers. The easiest way to fix it is to turn the volume up on the receiver and that seems to snap the audio back on the speaker that was a problem. Sometime the fix only lasts a short while. The problem has come up with different speakers at different times. Is this indicative of a dying receiver or could it be that multiple speaker connections are breaking down. Or is it all of the above?

sounds to me like you just need some contact cleaner on those POTS.
breakdown; there may be some corrosion on the metal parts inside the volume knob, there is special cleaner (this is an electrical device after all) that will remove that build up so the electrons can get through.

POTS (Plain Old Telephone System) or in this case pots (for potentiaometers)can become dirty with long use. Crackel, drop outs and sudden changes in volume are common signs. If you can't find an a cleaner for electronics try WD-40. Remember to unplug the receiver before you open the case.:)

hmm. Forgive my ignorance, but this would literally be in the volume knob? When I turn the volume way up, the sound kicks on, but then I forgot to mention, I can turn the volume back down and the speakers still work, for awhile. Then the sound drops out again later and I repeat.