I have left my ML loaded from Mid December to the next November, almost 11 months and it fired just fine. I have also had it loaded through snow, rain, constant temperature changes for weeks at a time and it fired just fine. My secret (and it's no secret) I always cover the end of the muzzle with masking tape, I believe this is the biggest factor in keeping moisture out of the barrel and having it fire when needed.
(BP)