My experience is that you have to refill it every time you want to use it. You say babies...does that mean they are in swim diapers? I know some people refer to their adult kids as babies, so I wasn't exactly sure of the age. ^_^ If they are in swim diapers, you HAVE to change the water every time. If not, the urine in the pool could grow lots of yucky things like bacteria since swim diapers only hold their solids and not the urine. However, if they are potty trained, you can always tarp it and use it for two days. I would never use it longer than that though. My daughter is constantly getting in and out of her little pool, so grass, bugs, and other yard debris will end up in the pool, too. This is really yucky after a day. I wish I had more help, but this is just what I have experienced. I hate feeling like a water hog, too!! I guess it is better to be a water hog and keep your babies healthy though. ^_^