Yah but how up to date a relays information is depends. So can lose data still if a major relay hosting most of your content goes down. Also say if you leave a relay that has data and choose not to use it anymore/get banned you wont risk losing what was on that relay. Correct me if I am wrong but I know relays can remove, filter, or totally censor certain things.
Discussion
there is no relation between "RELAY LIST" and "DATA RETENTION" - relay can ONLINE may have cleanup remove data DB file once a year. nostr relays are TX/RX NOT for ARCHIVE - that u need ur private/public relay whoever post there DB grows - user backup n retain themselves
That's is exactly my thoughts. So you can lose data if you do not run your own private relay...