Same as above really.
Know how much you use, and how long whatever recipe you're using takes to be vapable for you and work from there.
Most of what I do now is shake and vape, but most taste better after a few days to a week.
I mix in smallish amounts, only 50ml bottles, and one lasts a week or so, so 3 or 4 of those in different preferred daily vapes get mixed, and a week or so before they will run out I'll mix again, but it's more of a, eh look, thats nearly gone, I like that one, time to make it again.
Then I might mix up something different if I fancy a change in between, that will add another week to my supplies, do that a couple or few times and that's a month of extra juice to consume, this is getting out of hand, then you don't like the older daily vape juices much, so you mix your fresh juices and have these part bottles laying around, onmygod, what have I done, may as well just kill myself at this point.
As long as you have the diy stuff there and something you can shake and vape I don't really see the point in worrying about having a huge 'stock' of juice premade, although it usually works out there there is always something kicking around, I could probably stop mixing today and not have to for 2 or 3 months just by using up part bottles that are kicking around the house, even if 'older' juice isn't to my taste.
I see people mixing a litre of this and that and think, christ, long before I even make a minor dent in it I'll be wanting to vape something different, I don't know how people can have a single juice they use day in day out for months on end
