Twenty-four terabytes! I can remember a time when I had probably the hottest computer in town, the first 66mHz 80386 processor, a full 4 MB of RAM, and a monstrous 640MB hard drive. I knew I would be set for life with that rig, who could possibly ever need or even want more than that?

I mostly agree. Personally, I have a backup-dedicated NAS where I keep daily, weekly, monthly, and manual backups, AND I have a Crashplan account for "cloud-based" backup.

Still, I find RAID very convenient. Great to cope with mechanical failures, so much faster for upgrades with no down-time.

Yes, one may consider it relatively expensive overall, but is it really? Ultimately few hundred Euros every 10 years is not that bad for some peace of mind and a lot of time saved. I find that brings me a lot of value (subjectively, of course).

Well most of that space is taken up with movie videos (and also music to a much smaller extent). You see, every time I think I'm set for life, they come up with something new that just eats disk space. I once ripped all my DVD's. Then they came up with Blu-Ray. Now it's UltraHD (4K). Next: probably 8K... And also add HDR to that.
Although I do think there will probably come an end this this real soon now. See, it's already hard (for me) to see the difference between HD and 4K on a reasonable size TV screen. The difference between 4K and 8K will probably be almost non-existent to the viewer as long as they view it on TV's of 55" or smaller (which are most of the TV's in the living rooms out there). But hey, maybe they'll come up with holographic TV viewing or something. Who knows?