The last exactly as long as your dosing schedule predicts If you buy 1000g, and use 4g per day, it will last approx 250 days
BA, Common dose is 4g/day. Therefore 500g will last 125 days.
For Pre-Workout, we have the Ultimate Mass stack. But you can just mix your own creatine, beta-alanine, cit-mal, arginine, etc. Try searching for some of the terms + pre-workout