The problem is that while the number of pages steadily increases, only
the newest index files get updated, so as a result the link to the last
page is not correct on the first page(s).
You found a bug. MHonArc tries to minimize file I/O by only updated
index pages that need updating. The problem is that mhonarc does
not check if the last page has changed (note, by default, a link to
the last page does not exist in the index pages).
A possible fix is to have a resource to tell mhonarc to also base
index page updates by the change in last page filename. I am unsure
what would be the best name for such a resource (eg. USINGLASTPG).
BTW, to have mhonarc auto-detect if $LASTPG$ is being used would be
expensive since it would have to scan every page layout resource to
see if the variable is being used.
Note, you should be aware that everytime a new page is added to an
archive, all the index pages will have to be regenerated. This can
get expensive if the archive is large. A possible enhancement to
mhonarc is to support user defined actions during an archive update.
For example, if I can tell mhonarc to create a symbolic link from a
symbolic last page filename to the actual last page filename, then
one can avoid all the index pages from be recreated (assuming that
the index pages refer to the symbolic filename as the last page).
Just a few more things to add to the to-do list,