I feel like it might be almost trivially solved with a “buyer only needs one [for X months/years?]” property on the items. It would likely have to be added by

I feel like it might be almost trivially solved with a “buyer only needs one [for X months/years?]” property on the items. It would likely have to be added by a human, but still: there are a relatively small number of items that people only need one of.