I think you can click once a day only.
This is a great cause and I was going to post a link here, but Hell beat me to it
I have mine set up so they send me an email every day so I don't forget to visit and click.
I used to have them do it, now I don't even do a thing before I go there in the morning...that's the first thing I've done for the past three years! haha! First it started with just the Rainforest, then they put the Big Cats in, then the Pandas, now, the Fight for Breast Cancer. That was an easy enough climb, they have to put more levels on that one, but I just keep clickin' anyway...I love the site! I put it up here a while ago, but this time it seems to be generating more interest. That makes me smile!