How often do you need to have your fork and rear shock fully serviced? My guess is that this depends on how many miles you are riding, so lets say 150 miles/ year.
Most fork manufacturers will actually suggest service based on Hours on the fork, I know Fox will suggest you breakdown and clean all seals and replace open bath oil systems every 30 hours ridden. Also most sealed gas dampers suggest you send them back to the manufacturer every X number of hours to have them rebuilt by the factory.
- Obviously, this depends on the make and model
- Even more obviously, it depends on riding conditions, mainly on how much mud and water the hardware is dealing with
- "Fully serviced" is also an imprecise term, manufacturers may indicate different service actions with different frequency
- By caring well for the shocks (mainly by cleaning off the mud, and periodically cleaning gaskets etc.) you can extend the inter-service intervals
Having said all that, just to provide you with an anchor point: for a bike exploited almost solely off-road, year round in continental northern European climate, I would say a typical service interval for shocks/forks would be 2000-4000 km.