This shouldn't be an issue in the future, hopefully. Steam appears to issue 6 month session tokens now, and I'm fairly certain they should be getting refreshed on each login now. But I guess we'll find out in about 6 months if I didn't implement anything correctly 😆
One thing to note here, you don't need to drop the --recent flag if you want to also use select-apps. You can do any combination of select-apps, --recent, --top, etc. And it will prefill the combination of them all.
I've written up documentation to help with getting SteamPrefill setup with User Scripts. You can find it here : https://tpill90.github.io/steam-lancache-prefill/install-guides/Unraid-Setup-Guide/
Please let me know if that works out for you, or if there is anything unclear that needs to be improved.