That makes sense then. So by "empty" you don't mean barren with no furniture or anything. Just make sure it's the house with the homestead exemption on it. Also, it needs to be listed as your residence on your voter registration, as well as your driver's license and all that other stuff. It should also remain your billing address for your utilities, as well as your credit cards. Since you can just pay that stuff on line nowadays, that shouldn't present a problem.
But do be aware that if you have the electric and water turned off during your absence, that is the primary way the IRS will argue it was not your primary residence. It would be best to have someone stay in the place during your absense, as a house watcher maybe. You leave it empty and unmaintained for two years and I'm sure you're aware it will lose value as it deteriorates from mother nature. Besides, someone has to keep the grass cut anyway, right?
