The manufacturer's standard. You should pick a re-packer who has been certified by your raft manufacturer.
My guess is that the reference to the "inspector assigned to witness servicing of inflatable life rafts at the servicing facility" may be that for which the inspector wants to charge the $90, so maybe he's not ripping anyone off, he's just confused as to what type of boat the raft is going on. Bottom line is -- if the USCG doesn't require a raft on your boat, you don't need to follow their guidelines in inspecting it, and you won't need a USCG certificate from the inspector. That said, you should only use a repacker who's been certified by your manufacturer.
I'd recommend that you witness the repacking if at all possible. You'll learn a lot about your raft and be able to see all the gear that goes inside.
That's exactly it, very well put, good suggestion about watching the re-pack also.
I remember back in the 80's when I was sailing a Swan 44 around pretty regularly, the raft was due for re-padking and the owner of the boat said; Ok I think it's time for a life raft drill. We proceeded to act like we had an emergency and get the raft in the water and pull the rip cord, on a mooring in Newport harbor! I forget how long it took us exactly to be in the raft, but it was just a couple of minutes for the 4 of us to be in the raft with the grab bag. It was quite the experience, in a non-emergency...good practice.
Oh well, back to the question. Most manufacturers recommend repacking every year or 3 years, by a facitily that is certified by the manufacturer. It is important for it to be done when specified, because the more years you put it off, the more it costs, and then there might be the time when they say "sorry we can't repack your raft. If you are diligent you can get many years from a raft. Most times when I survey a boat with a raft, it is past due for inspection.
Keep you inspection current, you want to make sure it will open when you need it. Can you imagine needing to pop it open and finding that it won't!