We migrated some process instances with pending timers. The timers were defined with a long-running duration like P56D. However, their activity id did NOT change during migration, but was still the SAME. Anyhow, the timers were re-scheduled starting from the migration date. (The old timer jobs were dropped from the database, and new ones were started.)
In my view, it would be much more intuitive NOT to reset the timers—at least as long activity ids and timer durations remain the same.
(We use Camunda with Spring Boot, version 7.14, dependencies managed using camunda-bom.)