Unless you have a large family or eat a lot of eggs, 4-5 birds will give you more than enough eggs, especially with birds like Buff Orpingtons or Rocks. Mine lay 1-2 eggs per bird per day in the season. If times go really bad having a little excess will come in handy for bartering.
You really get 2 eggs a day out of some birds? I didn’t think that was physically possible.