I used to use the Five Star Io Star Sanitizer. It requires a 2 minute contact. It also stains all plastic purple, which isn't a problem, but just looks weird. I've heard it can't be kept as long as StarSan either.
I keep a 5 gallon fermenter of StarSan mixed up with an airlock on it. I re-use it. I've been told as long as it will still make bubbles easy, it's still effective. The bucket you see behind the carboys in the photo is that 5 gallon fermenter. When I finished I just put the lid on it with the airlock. It is my understanding, that if you leave it open, it loses it effectiveness more quickly. If you leave it covered under an airlock, you can re-use it for quite some time.
By the way, that photo was taken 4 hours ago. There are no bubbles left in either of the fermenters.