How long should babies have poopy diapers w/ most feedings?

My son is 7 weeks old and up until a few days ago had a poopy diaper about a half hour or so after every feeding. Now he's down to maybe 2 or 3 a day. He is mostly fed. 1 or 2 formula bottles every other day or so, when he's with gramma. He's eating more than before, so I know it's not that he's not eating enough. Maybe his digestive system is just maturing? Thanks for the voices of experience!