Yes.

The reason is that we have no real data about how many donations in any given hour will be enough to win the $2,000. So the trade off we decided to take is to increase our likelihood of winning a few hours, at the expense of having an even distribution over more hours. Since I'm happier to win a few by a landslide, than loose all of them by a hair. Also, more practically, coordinating the latter approach is much more difficult on a large scale.