Just checked my policy. Two exclusions apply when a home is vacant for more than 30 days. One, for glass breakage and one for vandalism. However in both cases, the exclusion applies only with respect to personal property. The portion of the policy that pertains to the dwelling itself has no such exclusions. The term vacant is not defined consequently it likely includes the term unoccupied.
When reading your policy, make sure you check both not only the insurance agreement, but the conditions and exclusions. Sometimes an exclusion is found as a limitation to an insuring agreement.
For those of you who don't want to spend hours trying to understand the coverage when at the end of the day, you've probably missed something, just ask your insurance company or agent. Make sure they respond in writing.