My initial belief was that I could assign a role and its expiration on a by-node basis (so as to create several different time lengths), but after some headscratching, I'm only only able to set a global setting at /admin/store/settings/products/edit/features, does Role Assignment not work on a node-by-node basis? I was expecting an option in the 'edit' tab of my product node.

I guess I'm just wanting more than there is?