I try to use my water as soon as I can after getting it ready and to the right temp. If you leave a container of water standing for a while it usually gets a film on top, which I think is bacteria and such. I try not to use the water if a film starts to form.
If your container is made of something like glass that will not leach anything into the water, and you keep it covered until used, I would expect it to stay in good shape for several days.