I am almost finished my second challenge already - I don't care if they extend the time frame but I like being able to do them one after another and I would hate to see that disappear because they made changes allowing for people to do more than one at once.
I do agree with your first point, there really needs to be some choice. Personally I would like to see the co-ops removed from this since the timing required to get people will only get worse at things go on.