"toban"......Typically once a year/15K miles for greasing the chassis. It has been recommended that the driveshaft be lubed every 5K, due to the stress (torque) these driveshafts see. That's a tough schedule to keep, but do the best you can.
You'll need to get a grease guide for your chassis or look it over front to back and find all the fittings.
There is a secret to lubing the driveshaft. Most of the u-joints have two grease fittings, one on each side. Either one will fill the u-joint. Just make sure you see grease coming out of each cap. The slip joint has one fitting in the center of the tube. They hold a lot of grease. As you fill the slip joint, grease will eventually run out of a small hole at the back of the yoke, between the yoke and the u-joint. When grease starts coming out of the hole, you need to get a finger in there and plug the hole. It's difficult to do while still pumping the grease gun. It's much easier with an air gun. Once you block the hole, keep pumping until grease comes out where the slip joint moves in and out on the splined shaft.
Don & Mary
2019 Newmar Dutch Star 4018 - All Electric
2019 Ford Raptor Crew Cab