J.B.
My first was bf for 7 weeks, then formula till he was 10 months and then straight cows milk-no problems.
My second was bf for 10 months then straight cows milk-no problems.
My third is now 5 months old and still bf but when she weans she'll go to cows milk too, as long as she's about 10 months old. All my kids were pre-term babies and the second spent time in the NICU, she was the earliest...we have lactose problems in my fam, but my kids seem to be fine & they LOVE their ovaltine chocolate milk.
My cousin has 3 kids and all were 38-41 weekers and she fed them cows milk from 9 months on. My brother was given cows milk at 9 months and is fine too.