I managed to bundle about five commands I used to run to keep my packages up to date, and not have those pesky "-opkg" config files left over in /etc/config that I had to manually remove, into a single big one!
(for those who don't know, -opkg config files are conflicts from updating, containing basically empty configurations, perfectly safe to remove as OpenWrt doesn't use them anyway)
I have ran this twice already in the last few weeks, so far everything is working fine. Make sure you have enough free memory as it's a large command.
Here it is:
opkg update && opkg list-upgradable | cut -f 1 -d ' ' | xargs opkg upgrade && find /etc/config -name "*-opkg" -type f -print0 | xargs -0 /bin/rm -f