Powder versus Ready to Feed (Premade)

We're formula feeding Libby and started her out on the premade/ready to feed formula. When we came home, we thought this would be easiest since we weren't used to a baby and the hurry up and feed her she's screaming scenario. It was great and worked out perfectly. Since the premade was what the hospital had, it was an easy transition. Now we want to try to get her to use the powdered version and that is causing problems. I don't think it is as thick or fills her up as much so she is really struggling with feedings. Sometimes she makes it an hour and a half and sometimes she makes it 2 and a half hours. It is just crazy. Jim did some calculations to see how much more expensive the premade is versus the powdered and honestly it isn't worth it if she is going to eat twice as often and as much. Some websites recommended to transition the littles ones from the premade to the powder that we should switch from one to the other at each feedings. We're trying it out but after 3 days on just using the powder, it is definitely rough. I'm hoping if we add the premade stuff back in she will go longer. I'll let you know how that goes. =)