Alternately, noting them but not sending them an email at all. Much like a gym membership, the people who don't use it at all but feel like they should someday

Alternately, noting them but not sending them an email at all. Much like a gym membership, the people who don't use it at all but feel like they should someday (as long as they're not nagged about not using it) are one of the most profitable subscriber segments. Sure, they'll leave eventually, but they're not using your service anyway, and until then it's free money.