itll be fine. i could see if it was stored in a damp basement or humid area, but jsut in a closet even a garage wouldnt affect any of the lube, orings. you wont damage anything by useing it as is. the only thing as mentioned above is the spring may have weakened by sitting half cocked, and the hopup may have been left engaged leading to the bucking being suashed. the only thing i would worry is that the battery was left dead and might be no good anymore. if it doesnt hold a charge you can try to revive it by freezing it and resetting the cells.
things that wouldnt hurt to do would be;
- new hopup
- new piston oring
- new spring
- new battery
and if you really want to get crazy;
- new cylinder head orings
- new air nozzle orings
most of these can be replaced via a kit.
http://www.airsoftparts.ca/store2/in...oducts_id=1105
http://www.airsoftparts.ca/store2/in...roducts_id=682 (few parts needed as well)
but the gun will be fine as is until your ready to replace these parts.