Why not have points begin to erode at a very small percentage of the members total after a certain period of time since last vote was cast.
This would encourage voting on a relatively regular basis.
I also like the idea of 20 votes.
My take on the game of climbing the ladder – I am generally not a game player, but it is interesting to watch my meandering climb up the ratings, with the occasional gain in power, it does add to the experience of being a member of the Monastery. If the scale is to become sliding because too many people have beat the game and now find it no fun, why not create another game that only people in the top ranks have access to?
An additional game at the upper levels would prompt those who need to beat a game or a system have something to look forward to, while leaving those of us who plod along lending a hand where we can, and gaining knowledge in the many ways the Monastery offers are able to keep track of where we are in the scheme of things.
One other point, any time you put someone on a scale, they will pay attention to it. I believe many people (myself included) will take offense to being randomly bumped downward just to make more room at the top of the scale. Personally if this is the route taken, I would like the ability to opt out of the XP scale.
What could the additional game be? Perhaps as suggested elsewhere in this post, XP beyond an upper limit in the highest rank can be used to buy additional powers. Things like signature options, particular home node modifications, option to put a picture in the front-page rotation, be able to buy various icons (also suggested elsewhere) or with enough points, the ability to post an icon others can buy for their home nodes.
Obviously I have no idea what effort implementation would take, but these are my 2 cents worth.