Do I have to live in Bulgaria full-time to keep investor permanent residence?

Investor permanent residence is attractive partly because it does not demand the same continuous physical-presence pattern as some other routes. Once granted, the status is intended to be indefinite, provided you meet its conditions.

In practice the physical residence card is issued for a set period and must be renewed when it expires, and you must keep your qualifying investment in place. You should still confirm any minimum-presence or reporting expectations with the Migration Directorate, since rules can be updated, and avoid letting your card lapse.