I leave fresh cold water all day and night long. I change the water in the morning, then hubby changes it when he comes home to check on the babies during his lunch break, I change it when I get home from work and then I change it one last time before I go to bed at night.
I also leave the air conditioner and fan on all day while I'm at work and the weather is hot and humid. Man oh man do I have some expensive bill during June, July and August.