even pre being "ill with hms" waking up by myself, i.e. without alarm, I always slept 10-12 hrs, could manage some days in a row with less, much less/even no sleep at times, but then would need a big sleep in or become foggy brained, hyperclumsy or would catch a cold etc
becoming "ill with hms" more and more need for sleep crept in- at my worst I totalled 16-18hrs out of 24 (including unavoidable day time napping)
...sheppey, like you I found no amount of trying to pace made any difference...at least not for years
and trying to fight sleep, not nap etc ...just wasnt poss, I d just end up conking out in/at the most inappropriate places/times...
but after some 5yrs in total ....I realized I d wake up "brain awake" ( body always takes a bit longer
to fully function) and that after some 8-9 hrs and that s my normal now
and weirdly...I was a total night owl, even as a kid, now...I m tired by 10-11pm, read a bit, fall asleep and wake between 7-8.30