I tend to start with the highest quality available and as years goes by if the "value" of that content diminishes I have no qualms about halving its filesize for a ~10% loss in quality if I need space for more valuable content. I use a high-quality Nvidia x265 encoder via ffmpeg that runs ~10x faster than my CPUs can. It produces slightly larger files for the same quality that CPU-encodes do, but the time-savings are worth it. Preserving a higher quantity of content takes precedence over quality, but obviously trade-offs are made based on the value of that content.

Before anyone goes chastising me, realize I've been doing this for 20+ years and have accumulated far more content than can be consumed across many lifetimes.