That’s a good point, and I think it should help preserve your notes. However, most relays don’t seem to have that as an obligation (i.e. they might purge notes that are older than a set amount of time).

Maybe check out this tool if you haven’t already: https://nostryfied.online

It’s supposed to broadcast your notes to more relays, but more importantly, back them up. Still on the lookout for how to use the backup file tho.

nostr:note12gvuejacf05h8jc97qmr98kaf8ndf30cguujzprj6f7xpvxcvnesytdxjq