understand $LOCATE_PATH=~/.locatedb and do... something better

Reported downstream on Debian. #1000429

catfish has a hard-coded path to mlocate's default database path:

https://codesearch.debian.net/search?q=pkg%3Acatfish+mlocate&literal=1

https://sources.debian.org/src/catfish/4.16.3-1/catfish_lib/catfishconfig.py/#L32

mlocate and plocate support $LOCATE_PATH being a colon-separated list of paths to locate databases:

https://manpages.debian.org/bullseye-backports/plocate/plocate.1.en.html#ENVIRONMENT

I use this to run updatedb directly on the NAS, which is MUCH more efficient. The commands are approximately this:

# on the file server, generate ~twb/.locatedb
sudo -H -u twb nice nocache updatedb --require-visibility=no --output .locatedb --database-root ~twb

# on the desktop, where ~twb is NFS and / is Debian Live
export LOCATE_PATH=~twb/.locatedb
locate foo
catfish

I think with Debian 11's catfish, it will ALWAYS pop up this alert:

The search database is more than 7 days old.  Update now?  [Update] [X]

I'm not sure EXACTLY what the correct semantics here should be, but the current behaviour is definitely annoying me! :-)