I buy by the gallon when I get my general hydroponics nutrients just because it saves me a lot of money. I use more of the micro and the bloom than I do the grow. So I might have one gallon of grow on hand and two gallons of the others. For me that lasts about 9 months to a year.
I've used the exact same nutrients in Hydro Coco and soil, so you can't really go wrong buying them. I also think they have a longer shelf life than other nutrient brands that intend to give you beneficials or Organics.
You might buy a quart of the grow and then a gallon each of the micro and the bloom. That would probably last you several grows. there is also a schedule where you don't use the grow at all, you just use the micro and the bloom. I believe they call that the Lucas formula. In general I find I can follow the schedule with those nutrients and autoflowers, the only thing is is I use less grow nutrients like one or two mils per gallon Less. then I use even less grow if I'm using a lot of General Hydroponics calimagic, it has plenty of nitrogen in it all by itself.
