how long let b sit before starting

I have an old Chevrolet van I have used for years as a camper. I park it in November (outside in Minnesota), remove the battery (or use a trickle charger) and don't start it again until April. That has work for 20 years. I do the same thing with my newer Dodge based B and again, I have had no issue getting either running in the spring. Be sure the tires are aired up in the fall and be sure to check them again in the spring. Park on a solid surface (not grass). I always change the engine oil in the fall before storing and obviously you want to have the RV well winterized before putting it to bed for the winter. I used to always fret about leaving the vehicle(s) sit all winter, but experience has taught me that fretting over this is a waste of energy.