Prune doesn't only write an archive when it has a full month's data -- so that means it might repeatedly write a particular month's archive, overwriting past archives in the process. Ugly.
It should either append to pre-existing archives, or it should only write an archive when it has a full set, or possibly even both. (Try not to write an archive 'til you have all the files for that month, but append to it if you discover later that there are more files.)
Prune doesn't only write an archive when it has a full month's data -- so that means it might repeatedly write a particular month's archive, overwriting past archives in the process. Ugly.
It should either append to pre-existing archives, or it should only write an archive when it has a full set, or possibly even both. (Try not to write an archive 'til you have all the files for that month, but append to it if you discover later that there are more files.)