The dry food will be fine at the bottom of the cage for months
I tend to prune the bottom half of the hoard and any loose stuff, when changing the substrate (usually after 3 or 4 months). With a litter tray and a good 4 to 6" of substrate, the cage stays clean and dry. If any hoard is pee'd on then it needs removing but then just put new food back in the same place to avoid major drama. Our robo buried food in multiple places and hamsters can have a few hoards (they especially do this if their house is cleaned out and their hoard removed as they get more cautious and have few spare hoards!).