You dont throw out the glass when the PEI is done. You buy a new PEI sheet, take off the old one, clean the glass, and stick on the new pei sheet. The only waste is the pei.

With metal sheets, when the pei is done, the metal could probably use replacing too to prevent warping. Otherwise, theoretically, the sticker method would work with metal too.

In this context, metal is definetely less durable than glass. Metal bends, metal warps, metal scratches. Unless your putting rocks on your glass bed, you won’t scratch it, and glass doesnt bend.