Auto-Renew

Auto-renew is the checkbox at your registrar that says "charge me and keep it" when a domain comes up for renewal. Most registrars turn it on by default now, and for a portfolio you actually want to keep, it should stay on.

It fails quietly. An expired card, a changed billing address, a registrar account with a dead email, and the renewal bounces. The registrar sends a few notices, then the domain expires like any other. A surprising number of good names drop this way, which is part of why the expiring-domain market exists.

The other side of the coin: auto-renew makes it easy to keep paying for names you'd never buy again. Once a year, pull the list and ask which ones you'd register today at the renewal price. The ones you wouldn't are costing you money.