Since we rarely have rideable conditions that you could call "muddy," service schedule is not as crucial. Muddy stanchions are bad news! I've seen fancy Fox Kashima stanchions scratched to hell because the rider didn't clean his fork and rode with dirty seals. I've also seen some forks that had to be replaced outright due to neglect.
Regardless of how important longevity is, dropping the lowers, cleaning the wipers, and reassembling with fresh bath oil should be done every 6-12 months around here just to keep the fork smooth. That basic service is darn easy to do with really basic tools. It just sounds scary because there are fluids involved. It's easier than bleeding brakes.
I can do my fork in about 20 minutes so it's not that hard. I know shocks are even easier but as a hardtail guy, I've never had to do one.