FWIW: My RS-11 "remembered" its re-programmed ID, day 2. Yet, given it lost it over time (from last year to yesterday), and given other people's experiences, I surmise it will eventually lose it again. It's not a big deal to re-program, but since this engine will be part of a lashup, it would be a PITA to have to re-program.
I don't understand how it remembers it's ID short term and loses it long-term.