How many bottles for breastfeeding?

First time mom here! I want to register for the breastflow bottles (avoids colic and nipple confusion) in both the 5 oz and 9oz sizes. Both come in sets of 3. Should I register for more than one set of each size?

I plan to take maternity leave for as long as I can (likely 6 weeks) then go back to work and pump. I want to exclusively use breastmilk (unless there is an issue) until 4 months then I'll begin introducing proper foods and hope to be weaned by 8 months. (Of course I'm a first time mom, so this whole plan could go on the toilet when baby comes and calls the shots!). What would you suggest for this plan?