A.M.
Having kids in things where they move in a way they aren't developmentally ready for (jumping in a jumparoo, walking in a walker, sitting in a bumbo) isn't best for them. Not that they are screwed up for life or anything drastic but the less time the better.
While it's not obvious to most of us, those trained in movement (like movement/dance therapists) can see the differences in how people move later on in life based on early physical development.