Since a Gallon of D76 develops 16 rolls of 36 exposure 135 film, regardless…
My whole life I have done 32 rolls per gallon bag of D-76.
That’s four quart bottles a batch*, two runs per bottle at 1:1
Quart tank holds four rolls.
I almost always use it all, even if it takes a few years. If I find a half bottle on the sink shelf after I haven’t been in the darkroom for a while I might throw it out. But if it’s only been a couple weeks I will still use it.
Only once in my life have I had a suspected “failure to develop”. But that could have been the famous “grabbed stop by mistake” trick.
It’s definitely less than Kodak recommended stock per square inch. I make up for it with longer development time. Standard time for me is 13:30 (TMAX100/ Tri-X, TMY2) to aim 0.62 CI.
*I mix water to give 8 ounces more than a gallon, each quart bottle holds 34 ounces and I top them off.
I won’t say it’s best but it’s certainly economical. NB23, you definitely process a safe quantity.