I think we should be able to overclaim plots that have been completely unused for 6 months at minimum.
I believe there is plot expiry for plots that have not been built on that are not protected as 'done' after a set number of days... I am not sure on the time limit however
I think as of about noon my time today, my time we actually JUST did this. :) Along with that, we're likely going to condense plots closer to spawn as well. Theres also a new method of plot scanning we're going to implement soon which will scan your plot for percentage changed. So if the player hasn't done much on the plot at all and its older than X time or the player has been MIA for X time it will clear the plot.
Na its likely going to have to meet all three requirements to be reset. So that we have a lesser likelihood of wiping out builds with our auto clean system.
As cham said it would be for more inactive plots with no changes and no site of the user online in some time. There is / could be a way to protect it like plotme has when it gets the bricks around it but I am not totally sure its enabled.
I don't think that were going to bother with protecting plots since we have the threshold method now.