Man, come on, one good batch at one store doesn't mean anything. Dollar stores get whatever's cheapest that week from whatever plant has extra, so the can you loved Tuesday could be a totally different supplier by next month. I've been burned too many times, grabbed a cheap can that was fine, went back for more, and got nothing but salty mush and rubbery chunks. The name brand at least has to keep the same taste or people stop buying it, that cheap stuff has no reason to stay good.

The timing thing is real, but nobody talks about what happens when you over wait. If you let that starter double and then leave it another two hours, it starts to collapse back down and get all hoochy on top. That stuff is acidic and it will eat your gluten structure before the oven even sees it. So the real trick isn't just watching for the double, it's catching it at that exact peak moment, like right when the dome is still proud and tight. I've had more flat loaves from waiting 30 minutes too long than from not waiting long enough, if that makes any sense. Your mileage may vary, but a quick sniff test on the starter before you mix can tell you a lot. If it smells like nail polish remover, it's already past its best window.