I'm unlearning some MnE to boost bard spell ranks. The "Time to Goal" keeps going up. What I thought would take 13 days, now is at 16 days. Can anyone explain this process in greater detail? Or point me to a place that can?

Thank you for your time.

And that's not a specific fixed 30-day period, it's "2,592,000 seconds, starting when you click the button to make things migrate."
(That's 30 [days] * 24 [hours] * 60 [minutes] * 60 [seconds].)

Ahhh, but at the end of each month (where 'month' == 30 days, so it happens more than 12 times per year [12-1/6th, actually]) the speed kicks up again.

Spell Research has the single highest training point cost in the game, so they will take the longest to migrate (either direction: dropping them to learn other stuff, or dropping other ranks to learn more spells). Most people usually recommend un/learning ONE spell at a time, so that you don't see ridiculous migration times for weeks on end.

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Also note, of course, that there is (now) an annual FixSkills that you can use to mass-reset all of your skills....