Thats what i wanted to add. Its more a "your identity" not a "your work" think with the nsec.
For the notes its actually the other way around. You have to care to have your work permanent. Either by paying a relay or running your own.
Discussion
Yep, though personally I think backing up one's own notes should be a function of one's Nostr client. (I am racist against web-client users.)
Also, the Nostr secret key is not always sufficient to protect your identity. You also need something like the time-stamp protocol to eliminate any possibility of man-in-the-middle impersonation bots.