Some carriers allow you to suspend liability coverage, which will be what you are paying the most for on a motorhome that old. Not on a per-use basis, necessarily, but seasonally. Good Sams insurance carrier is one to offer this feature.
Discontinuations of liability coverage will be reported to the state. How the state handles this varies. Some send a warning letter, some want you to turn in your plate, some put the license on a watch list. My state wants me to buy a "not used on the road" tag so that I continue paying fees. Considering that upwards of 40% of vehicles are driven without liability cover in some states, the enforcement mechanisms are not all that effective anyway.
On a vehicle that old, that low of insurable value, I lower collision/comprehensive cost by raising deductibles. When the value of the vehicle drops close to the deductible, I quit buying collision/comprehensive, as the insurer is not going to be paying anything on a loss. On an old motorcycle I had, the collision premium got close to the value of the bike. Not insuring becomes a no-brainer.
Tom Test
Itasca Spirit 29B