Oh ... I think I can help with this one!
From the Kellymom.com site:
"In exclusively breastfed babies, milk intake increases quickly during the first few weeks of life, then stays about the same between one and six months (though it likely increases short term during growth spurts). Current breastfeeding research does not indicate that breastmilk intake changes with baby's age or weight between one and six months. After six months, breastmilk intake will continue at this same level until -- sometime after six months, depending in baby's intake from other foods -- baby's milk intake begins to decrease gradually (see below).
The research tells us that exclusively breastfed babies take in an average of 25 oz (750 mL) per day between the ages of 1 month and 6 months. Different babies take in different amounts of milk; a typical range of milk intakes is 19-30 oz per day (570-900 mL per day). "
There is a great calculator on this page
http://www.kellymom.com/bf/pumping/milkcalc.html for estimating bottle amounts... but the main point here is that you won't need to increase your supply as your milk changes to meet a growing baby's needs.
HTH