I only just started using it a few days ago, but given how well the material is holding up (it's stiff instead of squishy like polyfill), I imagine that maybe once a week I'll pull 'em out, unroll 'em, wash 'em under hot water, roll 'em back up, and reuse 'em for months on end, or at least until the taste starts to change. My early impression is that they'll last practically forever. And you're right about the PG being helpful on the germ front. Eventually I may well switch to VG-only liquids, at which point I'll probably replace the PET more often.