How do avout matriculate to this math between aperts? While Stephenson suggested that avout can take the Labyrinth between the unarian-decenarian maths, I don't recall any indication that such labyrinths exist for other maths or would be navigable for the older fraas or suurs who might graduate to the millenarian math late in life. Notably, Orolo indicated that he would only join the hundreders upon the centennial apert.
In addition, if millenarian maths are generally filled during apert--and if the avout are sterile--how are millenarians expected to reproduce and repopulate their ranks? (Unless it's well-known to the hierarchs that the thousanders can extend their lifespans.) To some extent, this question goes for the hundreders as well.