depends on condition when parked not.unreasonable to find it dead. although i have stood the bike over winter and its been fine.
I wouldn't flatten it if it was mine. Although Steve is right that some can be recovered, flattening them can kill them for good. I also wouldn't leave it for much more than a month, ideally lead acid, gel or AGM prefer to be stored at full charge although cycling them does no harm and it can be argued exercises the battery. You could try raising a thread to see if anybody knows or can easily measure the parasitic draw from the immobilizer. If you have that info then if you don't have power where the bike is stored look into a solar charger as a possibility. I (like a few others on here) have a personal liking for CTEK chargers. Something like the XS 0.8 should be fine for charging/trickle charging and leaving on unattended.
