For what it's worth, Jill Bolte Taylor (author of My Stroke of Insight, which I recommend) said she slept 11 hours/night for a number of years (6, 7, 8, 9?) after her stroke. After that period of recovery, she found she needed only 9 hours/night. "Honor the healing power of sleep" is one of her central tenets re stroke recovery, and I would argue it applies equally to PCS recovery.