as we have no use for unused rebirth experience except use it in rebirth!
(boring) make it so you can use that unused rebirth exp as powerpool exp after
normal powerpool exp runs out
When you rebirth you discards all your exp, got it?
If rebirth had been in the game from day 1 people shouldn't even be able to
rebirth "twice at once" etc, but since it was introduced after some players
had more than 150m already I see one tiny point of having "rebirth experience"
in gam at all.