Here's the million-dollar question for me: will losing ED xp result in loss of unlocked twist slots? If I get to keep all fate points (or potentially earn even more than the current max) by re-leveling destinies, I might consider it. That potentially cuts out a *lot* of the re-grind; usually only two or three of the EDs are ones I *actually* care about; all the others I'm leveling (and being annoyed about being in, most of the time) purely to generate fate points for twists.
I'll take my Pale Master as an example. The destinies I'm actually using, between active use and twists, are DI, Magister, and Shiradi. If I "lock in" Shiradi, keep all my twist slots as they stand, and start leveling up DI/Magister again at 20, earning *more* fate points to the point where I can twist 4/4/4, I'm interested. If all fate points/slots are lost, too, then I'm out, and never TR'ing.