When "quick pickling" vegetables (submerging them in a salt + vinegar brine, but not properly canning them in fully airtight containers at high temperatures that would guarantee the product is free of pathogens), how long should I expect the vegetables to remain good if kept in the fridge?  On the one hand, I'm using non-airtight containers, doing my prep at room temperature, not sanitizing carefully, etc.  Basically all the things you shouldn't do if you're trying to properly preserve food.  As a result, I definitely don't expect these vegetables to last months or years like if I were doing proper canning. On the other hand, they're sitting fully submerged in a brine full of vinegar and salt in a refrigerator.  This seems like an environment that should be very inhospitable to most microbial life.  Surely this will cause the veggies to remain good for longer than they otherwise would, right?  I just don't know by how much.  The brine I'm using is approximately:  1 C vinegar 1 C water 1 T salt Other flavorings that I don't expect to make a difference, like some hot sauce and spices  The vegetables I currently have going are shredded cabbage and onions.  How long should I expect such quick pickles to last in the fridge? How should I expect them to go bad?  Will they mold?  Ferment and develop a mother?  Do something dangerous?  Just invisibly start tasting bad?  
Since you're putting the cabbage in a vinegar/water mixture, you are not fermenting it as sauerkraut (at least not initially), which would keep for months.  Instead, you're relying on the acidity of the vinegar for preservation.  The 50/50 mix you have there is plenty acid (est. pH of 2.8 or so), so even if fermentation doesn't start on its own it should be safe.  But for how long? This turns out to be hard to answer, even if we narrow it down to the most common recipe similar to yours, which is quick-pickled spiced red cabbage.  Online recipes advise from 1 week to 6 weeks, and there's no reason to believe those estimates are anything other than a rule of thumb.  The USDA is surprisingly ignorant of pickling anything other than cucumbers. The leading preservation books are no help either: Putting Food By does not cover refrigerator pickles for some reason, and The Home Preservation Bible says "3 days" (which is a bit silly since unsalted raw cabbage will keep longer than that in the fridge). However, there is one major difference between what you're doing and red cabbage recipes: you're using a cold brine.  Given that, there's no reason why fermentation of the cabbage wouldn't start on its own; basically, you're making an extremely wet sauerkraut. This also means that seeing bubbles is not a reason to think your cabbage and onions has gone bad; that could be fermentation starting.  You'd need to check, and see if it still smells sour instead of funky, yeasty or moldy, which would all be bad signs. 