Why 3-5? I'm arguing for one relay per user, and probably out of a set of popular ones. When you aggregate relays in an outbox model, you want to connect to as few as possible. The more relays the worse UX. This is how we lose.

An interesting alternative is to have relays that work as aggregators like filter.nostr.wine  

 1 is none 
2 is one
3 is redundancy 

 Because of different relay types and use cases for each kind. Ie inbox, outbox, search, backup, and private. 

 Sure. I am referring to relays to write notes to 

 I gotchu. I would then say that 2-3 would be good for most then. Most people would want a backup, anti-rug proof.