I don’t think This can be correct. It only doubles the period of 1m+ spells, to a greatest of 24 hrs. Implying that any spell with a period >12hrs would not be doubled, but fairly capped at 24 hrs. But a 1m spell only will become a 2m spell, and https://cashdrfrc.iyublog.com/20140060/about-dnd-multiclassing