Haha, I used to do this all of the time. "Whoops, need to buy more of this soon." followed by "Ah, I'll just keep vaping it - I'm good for now. Plus I have this flavor... and this one, and this one..." A few days later, I'd be sitting there malcontentedly vaping other flavors, just waiting for that next tracking update.
At the time, I was buying my favorite juice in bulk. I still do with certain ones because it's so cheap and I pass some onto friends and people at work... ...but generally, I just buy juice very impulsively. In a weird way, it kinda forces you to perpetually be up on your juice game. You don't ever have to worry about running out when you're always buying more.
It's also easier to not hold off on buying smaller amounts. No plans or routines. The routines make me complacent. I think when you buy a bunch, you kind of trick yourself into thinking you don't need to worry about it until it's too late. And other times, you get stuck with a bunch of juice that you're tired of. Better to buy a bottle here, another there, and maybe some of this along with it. I find I'm never low on anything that I'd otherwise be missing now that I'm taking that approach.
Besides, impulse buys often leave me with juice I don't expect to have. Who needs forced regularity when you can have self-perpetuating serendipity? Seems silly but it does work out for me. It's all about that constant juice flow. Tension keeps it all moving like it needs to.