Thank you so much to all of you who posted comments or sent emails with advice on baby bottles. Besides a few exceptions, the majority of people recommended the Playtex Drop In system. They make the nipples, bottles and liners all BPA free. Most all of the bottle companies make their bottles BPA free now, but this one seems to be the least maintenance. Because you put the milk in a liner, you only have to really worry about cleaning the lid and nipple, which cuts back on quite a bit of time. You do have to buy liners, but a thrifty friend of mine told me she just washed her liners in the dishwasher and that worked great. Also, another friend told me that she purchased off brand liners at WalMart, and they were less expensive.
I tried the bottle out on Olivia and the liners really did collapse, which proved to me that air was not entering back into the bottle. She seems to like them, so hopefully little baby boy Hewitt will as well. Thanks again, ladies!