I came home from a long trip in October 2014 and changed the engine oil(synthetic) It has sat other than local trips to and from storage and to get maintenance. I have started it up every month or two...
If you had let it set, right after a change, for two years without ever starting it, I would say the oil is OK.
But if you've been starting it every month or so, without getting it up to full operating temperature for at least a couple hours, it is probably loaded with acidic condensates. Change it.