Hang on to it unless you need the $. I am in a similar situation. We go a few times a year and are buying a house. It would be nice to sell the camper to free up the money for monthly payments, but on the other hand a few more years and it's paid off. Look at how many more good years of use the camper can give. I can't see how sitting could really hurt it. Cover it to protect it from UV damage, maybe set it on something to take the weight off the jacks. It wouldn't bother me to store mine for a few years if I didn't have the time to use it.
2007 Chevrolet Silverado 2500 HD crewcab, Duramax