No matter how you look at it, IMHO, you can't get enough of the good stuff into a juice unless you are starting with a concentrate. I suppose that theoretically you could make a batch, retain the VG and use with more raw material, and repeat.
I'm a pretty consistent stoner. Granted I still smoke some but I would guess I use about 2 ml of my thc vape juice per week at most. When I only smoked, I used about 8-10g per week. When I make my THC juice, I use ethanol (QWET) and do two pulls. The first is a quicker wash that I air dry. The second I do a bit longer and use for RSO.
If you like couchlock, Vape Juice made from RSO is great. I use it for sleep issues. And it stays in solution with separating much better than the air dried for some reason.
Avoid VG altogether when doing this. The main things people seem to use are straight PG, PEG400, and the aforementioned EJ Mix which is a blend of PG, PEG200,PEG400 and PEG600. Pros and cons.... The oil and PG separate fairly easily. The stuff still works though. PEG holds better. EJ Mix holds perfectly. But, for me anyway as others seem to feel differently, PEG has a bad flavor. Very chemically. I also think it produces a harsher hit.
I have been experimenting with how little EJ Mix one can use, supplemented by PG, to get something to stay in solution. I made a batch a few weeks ago with 1 ml of oil, .25 ml of EJ mix, a 2 ml of PG and it has held perfectly. But the flavor is still not the same as with only PG. It loses the hash oil flavor altogether and I like that flavor!