The good thing about nostr is that, contrary to popular federated protocols, your identity is not tied to any single server, you own the keypair to your account, so you can continue using it just fine even if some relays experience a downtime.

until one day when a quantum computer comes along, then goodbye your control of your nostr identity in both the future and the past!

If any major nostr relay goes down, no one notices. That has happened many times, the network is very resilient to that.