I've always used a loose-fitting lid. The fermentation process causes gas to form and it needs some means to escape, if only slightly. I would guess that a tight-fitting lid would pop/blow off in time. I usually use a big old glass apothecary-type jar. That's always worked very well for me. I've kept the mixture around for years with no problem. However, gotta be careful where you store it. It's so full of sugar, ants LOVE IT. Just a word of caution along those lines.
My recipe is a bit different from those I've seen posted. I'll post it tomorrow. It's beddy-bye time here in the Heartland of the USA. I'll turn into a pumpkin if I don't get to bed soon.