There is no developer-published threshold in the sources reviewed here that tells every player when to rebirth. The method below estimates a scenario from entered measurements; it does not supply an unknown game multiplier.
Use one measurement boundary
For the rebirth path, record Power when recovery ends. This is your total when the sustainable post-recovery rate starts, including any Power gained while recovering.
Do not combine Power immediately after the reset with a rate measured only after a longer recovery unless no Power was gained in between. Otherwise, the estimate can count recovery progress twice.
Compare both paths
Continue minutes = max(0, Target Power − Current Power) ÷ Current Power per minute
Rebirth minutes = Recovery minutes + (Target Power − Power when recovery ends) ÷ Power per minute after recovery
Use the second formula when the target remains above the recovery-end total. If you reach the target during recovery, you need the actual time of that crossing for a precise comparison. The recovery duration alone cannot reveal it.
Build a valid comparison
Choose one target relevant to your current session. Keep it unchanged between the two paths.
For continuing, use your current Power and a representative Power-per-minute rate without changing your setup.
For the rebirth path, identify the recovery duration, the Power total at its end, and the sustainable rate that starts there. An unobserved post-rebirth path is a what-if scenario, not a measurement.
Compare the two total times, then reconsider the inputs whenever your setup or rate changes. A larger multiplier alone does not settle the decision, because recovery still costs time.