Here's what I've done in my research. THC dissolves very quickly in many common solvents including alcohol, acetone and butane without the addition of heat. In fact when making honey oil with butane, the release of butane brings the temp of the weed down well below 0*F and in fact evaporates so fast that the weed comes out "freeze dried" at the end of the extraction.
The issue when using alcohol (91% from CVS) is that chlorophyll is also highly soluble so many hash oils made from alcohol are a dark green or black tarish looking (at least mine does) so I only let my weed sit in the alcohol for no more than a minute before I strain it through a coffee filter. I do this twice and I get a much more golden green color. I also leave the the weed in the freezer at least over night to reduce the solubility of the chlorophyll (I think I read that on another site).
I believe that THC activates at 170* F (at this point it will make you high in almost any form of consumption). The optimal temperature for vaporization is around 350* which is well below the 450* combustion level of plant material.
I use a vaporizer for 90* of my consumption. I currently have around 2 oz. of "spent" weed that I plan on turning into hash oil. I can either smoke the oil, re-disolve it into any liquor (haven't tried it). I've also dissolved the oil into melted butter and baked several goodies. It works pretty well.
Sorry for the ramble but this God's Gift sativa hybrid I'm on makes me just ramble about shit!
Typing at > 100wpm also helps too.