I stopped trying to do that when I saw my open rates for E-mail. I consider myself lucky if I get 40% of people to open an E-mail, and some E-mail updates get an open rate of as low as 11%. Depending on what the Borg Filter (Google’s Gmail) decides, your E-mail will either reach the users Inbox, or land in a dark place to be ignored forever. This means that any kind of “reaching out” makes little sense.
But on the other hand: why do I really care? Why do I need to remove accounts at all? I’ve designed my system so that an account costs essentially nothing. If people want to sign up and then not use the system for years, why not?
All this is obviously valid for free/freemium accounts. For paid subscriptions I do suspend the accounts fairly quickly if the payment is past-due, but then for paid subscriptions I don’t really want people’s money if they don’t use the app anyway, so this case is very different.