We had to do it with my son. He needed the thicker formula, otherwise he would be miserable. They actually put him on the AR (formula with rice added) while he was in the NICU because he was not keeping anything including breastmilk down. We did that for 2 weeks and then we started to add cereal to regular formula for every other bottle. It made such a big difference for him. When he was not getting it, he was miserable. We were able to stop it by the time he was 12 weeks and just use the Zantac.
I trusted the doctors involved and I know it made my son a much happier baby.