all4me-
I take it that you have looked at the past posts of all the hub leaders (especially the ones you have decided should bow out, which are???) and have weighed their contributions. What rating system are you using? Seriously. It seems that you are advocating using a simple "time from last post", or in computer-ese, a Least-Recently-Used algorithm.
My understanding is that there is no limit to the number of hub leaders. The fact that there are 40+ hub leaders for this hub indicates the amount of time the hub has been active, the amount of interest in it, and the stars and votes of the people who found those posts to be quite beneficial.
Why should those past votes be thrown out? Seriously, why? How is it harming the hub and/or you?