In the Boxster In Winter article
here . While it applies to winter storage, many of the suggestions advanced over the years are applicable to any long term storage.
Pull the battery and give it to someone to use, buy a new one when you come back. Don't use the battery maintainer for that long. Keep some form of insurance. Seal the exhaust pipes, both side air intakes and partially open front hood with painters tape to keep critters out and yet let you into the battery compartment. Clean car, polish it and cover it with a soft breathable cover.
On return, drive very gently to a mechanic after replacing battery, removing tape and resetting tire pressure. Then change oil, change brake fluid, and again reset air pressure in tires.
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