Just found some very old Miracle Gro. Any good?

We're in the process of renting out one of our homes and in packing things up I've come across four unopened bags of Miracle Gro, the water soluble powder stuff. I don't use that anymore but was considering giving it away to someone who does. It must be AT LEAST five years old, maybe older. But it's been kept in a dark, cool place.. Any opinion as to its efficacy after this long? Thanks.