I have some old, roasted coffee beans that have been stored in (mostly) airtight, opaque containers. The coffee beans are of reputable brands and are 2-6 years old, depending on the bag. They do not smell stale, but the flavorful coffee smell is mostly gone or barely there.
I am wondering if I can reroast them myself at home and still use them in my espresso machine or if I should throw them out. The reason I have so much unused coffee that's so old is that I stopped drinking coffee for a while, but now I am back and would like to give it another try.