In my garage it would last 2 months, as I have an insulated garage and keep the feed off the floor on a pallet inside a metal garbage can. Personally I would not keep the feed for 2 months in a hot shed where temps get up to 90s or 100s for that long (if that is your setup). Some sheds get very hot and some don't LOL.
Vitamin deficiencies in chickens are not pretty and the high heat would degrade the feed too much for my liking. But use your judgement and what works for me might not work for you so to speak.
It gets about as hot in my shed as it does in my house - Hot. We don't have AC, just so you get the temperature straight ;) I could put it in our storage room during the summer - it's the coolest place in the house.
Sometimes bugs hatch out in feed...you'd not want them to hatch out inside your home. Just FYI.
Hmmmm... Good point. Even if the bag is sealed? Once I open it it would be in my shed. *shivers*