How long does a 1 pound bottle of black powder typically last you?

It depends on what you are making with it. Flash powder you could use it up in 2 or three mixes. (Never make more than 1 pound at a time unless you are a manufacture) It will never really last more than a show, if that. If you are shooting balls with it, then that is another story. Many people will make their own, because they want to have the hardwood charcoal. REALLY should talk about this on a more secure site. For good fireballs never use more than a quarter inch at the bottom of a 5 gallon bucket, and make sure that you bury all but about an inch with sand, otherwise the burst gets spread out too much. Dry calf supplement is the best, because the protein content is higher. Dry milk will do. I want points for this, not everyone will tell you how to make fireballs.