Whenever! (well…… nearly!)
From birth to the day you don’t want to any more. For some it lasts for a few months, for others a few years. In some cultures, the elderly are also carried. One is never too old to be carried. Our children may become too tall or too big but a quality carrier will feel comfortable for both the wearer and baby. You also build your strength as your child grows.
For some it is a way of life, for others it is just once in a while. You can carry as much or as little as you want. Like everything, it has to work for your family.
For some it is only when out and about, in the same way one would use a pushchair, for others baby is carried for most of the day. Carrying is not an all or nothing activity, you can vary the amount of carrying depending on everybody’s mood.