I got some milled grains as part of two kits I ordered. I brewed one batch up last weekend and have one batch left to do. I've had the grains for about 3 weeks, but won't be able to brew today. How much longer will they last?
Definitely. What happens over time to cracked malt is the evaporation of aromatics. So over time you lose flavor but unless you get mold from improper storage you won't pick up bad flavors from old malt.
I kept grains sealed in their bags in the fridge for a month & they worked great. So you should be fine. Ant portions I don't use stay in there bags,resealed,& put in a zip lock freezer bag in the fridge.
Not sure how long they last. I have a Belgian recipe that I had milled about 18 months ago. I plan on getting to it this week! I kept the grain dry and will throw a pound of fresh milled malt in there to brighten it up. I really don't see a big decrease in freshness or conversion power if it is kept in a good container.