Susan,
 I would vote for any bf is better than none. I would explain to the moms
based on a dose-response model. The more bf the better for baby in nutrition,
immunology, infection protection.  The more formula the more illness etc.
There are some studies to support this. (Anyone have the refs?) This should
encourage them to use the least amt of formula.
Laurie Wheeler, rnc, mn, ibclc
violet louisiana