If you want to automate look into the "Wikiarr" but to answer your question I think many of us are just data hoarders. I try to delete stuff I've watched but I also tend to keep stuff that I've had trouble finding good versions of. I am also building a large music library (currently around 200-250gb) and that's entirely around avoiding crappy streaming services. Most of this collection I either already owned (used to rip ipods id repair for people) or used soulseek/other tools to build.
Personally I'd replace that 10 year old drive as it's probably limited on remaining life even if only lightly used.