I generally shoot a fouling group before a season. Just on the off chance that something shifted while cleaning, I want to check it out. So say I'm at the range, shooting groups and range-patterning my load (confirming my field card), I'll finish up, clean it at the bench, then shoot another group to confirm it's on track.

Personally, I'd be hard pressed to say that leaving a bore dirty for 30-60days will hurt it. I'm not sure my grandpa cleaned his rifle in 30-60 YEARS!!