Well often times along with a LTC there comes derealization and depersonalization and sometimes something called HPPD, where you have many feelings of still being on a drug. I guess a long term comedown basically is a comedown but just very drawn out, but if you have derealization and depersonalization bad after rolling then that's a sign it's more likely to become a bit of a LTC. Normally most people get an afterglow and comedowns can even be pleasant.
But just because you have a bad comedown for a couple days or even a week or two doesn't mean you'll have a LTC.