I have around 300ml of B&M bought stuff from when I started that is just no good, around 150ml of HHV (which may be my last vendor bought juice as this latest tobacco batch of DIY has proven very successful for my tastes) and around 400ml of DIY most of which I really like, some failed experiments but I am going to give them a while to steep to see if they improve.
Have around 100ml of just the Boba's Bounty clones I am trying, most of which are actually very, very good in their own right even if they are not Boba's.
On average, I would say between 200 and 300ml on hand at all times between the two of us. I make 50ml bottles of the juice we use daily.
I don't make very large amounts at a time as we are gradually lowering our nic levels, I am at 8, she is at 4. Also I have found that if you mix a fresh batch of juice in the same bottle with some of the old juice left it mixes well very, very quickly and hardly any steep time is needed.