Three things that have bitten me recently:

1. beware of encryption, especially Microsoft and Apple. I've encrypted Apple disk images with lost passwords, and USB drives that I'm not sure I'll ever decrypt now that I've mostly moved to Linux

2. USB drives rot. I have at least one sitting on my desk that doesn't work, or doesn't work with Linux, or is encrypted, I can't tell but I think it's dead and I've no idea what's on it

3. assume anything other than text or open formats will be useless later. I've a ton of info archived in closed proprietary formats that I might never be able to access.

Duplication is inevitable. I've a box of CD/DVD archives, a dozen large USB drives, two NAS, and half a dozen computers, and with all that storage and space I can't even have a definitive music collection. It's on both NAS, multiple computers, an MP3 player, my phone, and all the copies are different. We've 14 terabytes of photos, and so I now need to buy another NAS to replace the two I have and keep the old ones as a backup. It's endless curation, both for hardware and data.

And yet, the code I've lost. The photos that didn't make it to backup. I have those regrets too, like they were truly valuable.

Final thoughts: cloud storage isn't storage, it's short term for shuffling data between devices. Even email isn't secure - Yahoo deleted all my messages without warning because I didn't log in for a year.