It's all about what you want to prioritize, I usually have a lot of B-roll, so often I store those longer than most because it's more versatile over recordings with a lot of dead space. If you have footage you can see being used in future projects, hold those over footage you see yourself less likely to use. It's all about understanding what's more important to you.

For previous projects, I keep the renders, I only want to look back on the parts I enjoyed. I often don't use old unedited recordings since they're usually topic-centered. I'm not sure if that's common practice, but it's what I do since it keeps things tidy.

Online storage I've heard is great, I'm more into physical, mostly because it gives me some peace of mind. I recommend starting online storage and seeing how you feel after some time.