I'll give a bit of a brief history for me as this is my second time around being a somewhat "working mom" while nursing. B was the same age as N when I resumed my coursework after he was born. That being said... B did not need to have formula much at all until he stopped nursing when he was around 8 months old. With him I was only gone for two 5 hour time slots/week. Also, with B being a preemie we invested in a super duper double electric pump - the Medela - which I HIGHLY recommend to any moms that need to pump a lot or that have preemies that are not able to latch on effectively for the first while.
This past week was my first go at it and I hadn't yet gotten out the hand pump (Avent) I borrowed from a girlfriend so it was a couple of somewhat uncomfortable days followed by a slight dwindling of my supply. Also... N seems to pound back the milk I pump when it comes in a bottle so both days he motored on through all the milk I left (even my frozen supply). Since I feed on demand, it is hard for me to pump out large quantities. Consequently we were forced to supplement since I just wasn't producing enough when I pumped to meet his needs while I was away. With my own allergies, I didn't want to take any chances so we settled on a soy-based formula which doesn't seem to give him stomach troubles. He also started on rice cereal - just as his brother did when he was the same age.
I really wanted to hold back on starting his solids since B has so many allergies and I do as well. But when given the choice of a formula feeding or rice cereal I feel a little more comfortable with the cereal option. I just don't understand why there are so many fillers in baby formula. A girlfriend of mine weaned her daughter onto goat whey - when she was closer to a year though. I'm going to have to do a little more research on this one.
In the mean time... I have gotten the hand pump and cooler pack out for this week. I'll just have to find a quiet corner of the bathroom on my short breaks to keep the supply going!