It's all about the size of their legs. My girls had fairly thin legs so we used them up till about 2 1/2. We used them for story time, snack time, song time etc. I loved mine!
My girls did not like sitting in them. I used them until ~7 months adjusted, but never for a long stretch becuase they'd get ancy. Now they can sit up on their own, there is no need for it and they don't like being confined.
My kids started using them at 3 months. ?Now, at 6 months, they are sitting on their own and we don't use them as much. ?I have 3 of them, however, I wish that I had only bought 1 or 2 since they rarely all use them at the same time. ?
Re: bumbo seats
Still using them
Kerri