I don't use a regular back belt....I use a dipping belt for chins & dips, tho....but I don't think that's really what you're asking.
About 6 months ago, I was a big proponent of belts, because I felt it added stability to the big lifts. In reality, it made me weaker and more vulnerable to injury because I was able to lift heavier weights than I could have otherwise. In other words, the belt helped compensate for a weaker lower back.
So, I ditched the belt, and spent the last few months gaining strength in the lower back, and now, short of injury, I can't see myself ever using one again.
Also, I think there's a common misnomer about what the back belt was actually designed to do. The back belt was never designed to be a support system, per se. It was merely a method of keeping the lower back muscles warm & loose during exercise, especially those with manual labor jobs who have to hump it for 8-plus hours per day in colder temperatures.
IMHO, using a back belt as a means of added support will do more harm than good in the long run. If you feel you need a belt to do your big lifts (aka, your low back gives way), then I would add some good mornings & hyperextensions to your routine, and work those low back muscles until they feel like two pieces of rebar sticking out of your buttocks!