Cereal with formula?

My little one is almost 4 weeks old. I’ve read plenty that says you shouldn’t add cereal because of this and that or you shouldn’t do it until 4+ months of age. However, I’ve read plenty and heard plenty from parents who started adding very very little cereal to one bottle in the evening around 5 weeks of age just to help their little one sleep a bit longer. I don’t need people biting my head off, I would just like some opinions and to know your experience if any of you have done it. I’m not big on cereal in general but please give me your opinion!