Simply change the timer to suit. For my use case, it is sufficient to activate once only, 5 mins after boot.
/usr/lib/systemd/system/pkgfile-update.timer
[Unit]
Description=pkgfile database update timer
[Timer]
OnBootSec=5min
[Install]
WantedBy=multi-user.target
@Chrysostomus’s version gave error at boot and shutdown when no internet connection (because too soon, or too late):
[FAILED] failed to start pkgfile database update
That was on a fresh install, so I imagine a novice user would be disconcerted by that!