i have never heard that there should be a limit. i was going to say it depended on the child. some really like their walkers and learn to walk real quick. some don't like them at all or just don't care. now if he is just sitting in it and seems to not move at all with it. i would probably not even put him in it at all and wait til he got older and try again.. i had a baby swing and my youngest son loved being in it. i would take him out and he would cry and reach for it. so i must admit i would leave him there. he just loved it so much. it wasn't like i left him for hrs but for sure more then a half hr and i left him if he fell asleep. no side effects either. rarely used the walker so this time around i don't even want to get one.