We have accumulated a lot, I think!

13 five ounce Medela's
3 eight ounce Medela's
3 five ounce Avent's
8 ten ounce Avent's
10+ small bottles that we keep individual scoops of formula in so we can mix bottles at home quickly.
(Plus my in-laws keep their house stocked with more Medela's and Avent's there - probably another 10 bottles total)

We combination feed breastmilk and formula. I also WOH. So, with that being said all the bottles get used!