The "add a bunch of relays so you get more reach" is a leftover mentality from when relays were quite basic and general purpose. Now we have the outbox model in many clients, so that even if those who follow you haven't selected ANY relays you are writing to as "read" relays, they will still see your notes, because their client will look for your relay list and pull your notes from the relays YOU say that you write to.
Additionally, many folks are reading from relays that aggregate notes from other relays, after filtering for spam, such as nostr.wine, or nostr.land, or even their own Web-of-Trust relay. You don't need to actively post to these relays, as they will pull your notes in from wherever you are writing to, so long as you are writing to one of the relays they pull from.
The more relays you have listed as "write" relays, the more places Nostr clients have to look for your notes using the outbox model, slowing down the client and using a LOT of bandwidth. Realistically, after the first 3 or 4 relays, all of the notes received from the rest will almost certainly be duplicates.
If you are concerned that some people who aren't yet following you might not see your notes if they aren't reading from the relays you are posting to, then the answer is to use a blastr relay such as filter.nostr.wine as one of your outbox relays. You can also run your own HAVEN relay, which has a blastr feature. These relays automatically rebroadcast your notes to a set list of relays without those relays needing to be in your relay list.
