I completely forgot about the curve but I'm in favor of going to a more linear curve. I agree that its more fair overall. I'm also in favor of eliminating the 5 min window. The 3 stage window sounds fine to me but I see your point about keeping it simple. On a positive note it seems like the 3 stage creates an incentive for people to use the site each day. Active users are rewarded more so than people who come and go.