I've had a 5# tank that has lasted me 10 kegs so far. I just checked it last night and still feels like there is some weight to it but I expect it to die in the next keg or two. My first few tank fulls didn't last as long but I think I was wasting alot of gas during cleaning etc. I do a siphon now and don't push any cleaner/sanitizer through the lines. Seems to work fine. You'll get used to dialing things in pretty quickly.