This is kind of a complex topic... How long you let it sit, and what impact you're willing to accept as a result, is subjective. Keeping batteries charged, and making sure every. single. drop. of fuel in the system is fresh and treated are great things to do. But just because "it fires right up" doesn't mean that sitting hasn't had an impact on things like seals and tires. Seals last longer with exercise to stay pliable. Tires last longer when ran to keep the oils leaching to the outside surfaces to keep them from cracking. I'd be uncomfortable letting mine sit for more than a couple weeks at a time without driving it for an extended time at operating temperature. When you drive it, work everything you can. For example, if you've got an airshift t-case, engage it and put a mile or two on it loping through the neigborhood to keep the pinion seals, etc. exercised.