In terms of material, I use the most archival paper mache possible. Specifically I use PVA glue and acid free paper for the majority of the work. The antique papers are sealed with a UV protector spray made for preserving archival papers. The whole thing is built out from an interior wooden frame to provide structural integrity for hanging and support.

All this is to say that aging in paper is somewhat inevitable but I take all the precautions to make sure that process is incredibly slow. As long as it remains out of consistent direct sunlight there should be no issues.