Isopropanol has a fairly high boiling point, so it takes a little longer to evaporate it off. I prefer hexane or acetone. Ethanol works well, and you don't need 95%. Anything over 50% works well. I once made a tincture using cask strength (53%) scotch. It was delicious. I decarboxylated it...
THC doesn't appreciably degrade or evaporate in 30 minutes @ 375F. I've tried heating oil at 175C (350F) and 225C (435F), and saw little (if any) conversion to CBN in 30 minutes. A friend of a friend told me that an hour at 300C (570F) will fully convert THC to CBN, but I haven't tried that yet.
I use cannabis mostly to help me sleep. High CBN strains work especially well, but are not always available. Has anybody seen info on how to convert THC to CBN? Heating is supposed to do it, but what temp and how long to increase CBN content to (e.g.) 1%.