I can only speculate on length of use but I am using the Yepp until he outgrows it. At almost 14 months, he is fast outgrowing it. I just like having him at the front and listening to his humming. Also, I can easily monitor him. I also got a windscreen for him for those windy days, hahaha.
We have a 1yo and I already have a Yepp Mini Front seat setup for him. I am asking my wife if she would like this seat for her bike. If there are offers, please go ahead. I am waiting for a reply.
Dibs