Quite truthfully, I don't know when you can start to do both.
But from experience, I would do it as soon as you are allowed. I didn't in my first pregnancies and I had a heck of a time trying to get my babies on bottles. This time around, I will be getting the baby on a bottle as soon as possible.
Plus, my hubby felt left out with my first two. Also it was somewhat hard on me as I had a newborn and an 18 month old. I could only feed the baby and felt like I was sitting for hours in one day breastfeeding. I think my 18 month old felt left out (attention wise) and didn't get much attention as she probably should have. It would have been so much easier had the baby been on a bottle.
