I just made a nice fat chunk of BHO out of the larfy buds and frosty trim from my harvest (I use the stems and all the not-so-frosty trim for cooking oil so I'm not wasting anything at all), and I got 16 grams of way tasty and potent oil out of 8.5 ounces of trim...
I don't specifically designate any of my plants to go to oil, but once we are doing better I probably will... right now, we gotta make sure the bills are paid first. Eventually we probably will though, because my wife and I medicate exclusively with oil, and these 16 grams will probably only last about a month to a month and a half...