My schedule is as follows,
Oil and filter every 6k, all Fleetguard and Delo
Fuel filter also every 6k again Fleetguard
Every year or 24k the transmission and rear end gets a dose of RP
The BHAF gets changed every year or 24k
Anything with a grease zerk gets hit at every oil changed with Lubriplate 1500 series.
Everyone differs in their shedule, mine may be excessive to a point but it works for me and is a good investment to help everything last a long time, IMO. The way the prices are going for 3rd gens I need mine to last a very very long time.