I would advise the enterprising hash oil extractor to look into using naptha/pentane/hexanes/heptane as an extraction solvent, instead of butane.
As for butane choice, the standard test for any extraction is usually spraying some solvent on a watchglass and watching it evaporate. Residue is no good.
Butane BP is -0.5C.
Pentane BP is 36C.
Hexane is 68C.
Heptane is 98C.
Petroleum ether (mixture of hydrocarbons) normally boils either 40-60C or 60-80C depending on grade.
Pros: You're working with a liquid at room temperature.
As the hydrocarbons get heavier, vapor formation is less and less of a concern.
Can recover the solvent almost completely by simple distillation = cost savings.
Presumably cheaper and easier to get petroleum ether in bulk than any other hydrocarbon solvent. Hexane is also pretty cheap.
All linear alkanes have similar solvent properties, going from butane to hexane will not change the profile of the extract much.
Higher operating temperatures are permissible = higher yielding extractions, conducted faster.
Higher contact times between solvent and plant material are possible (you can stir the solvent and weed in a pot for 20 min, not so with butane)
It's maybe a little less suspicious and easier to store a few tins of naptha or bottles of hexane rather than dozens of cans of butane.
Cons: Requires more than a warm afternoon to remove the solvent completely (either heat or vacuum or both)
Still flammable. Hexane in particular can build up static charge.
n-hexane is a chronic toxicant that you should limit exposure to.
Pentane and heptane are more expensive.
Still dangerous goods.
Some fuels may be dyed.
Finding a sufficiently pure solvent that boils at the desired range may require trial and error or use of the Solvent Database I linked earlier. Varsol is not the same as naptha.