Baby carrier: until what age?
It depends on their needs, on the availability of the wearers, on the particular history of each family, on the environment (countryside, city), the culture... Basically, everyone has their own babywearing experience, there is no norm. There are nevertheless some rules. Each family will choose whether or not to extend babywearing beyond the first months where it is most obvious and expected. Babywearing, at least as we teach it, is a matter of free will and trust, welcome to parenthood
Generally, we carry in front at the beginning of life, usually at home, or elsewhere if you travel, work... During these first months, babywearing meets an important need of the infant. When Baby discovers their motor skills, they'll want to spend some time on their play mat, we'll start carrying them a little less, typically on the hip and on the back to free up their field of vision and hands. Time will pass, one day you'll certainly feel guilty about carrying them too much, putting them to sleep in the wrap, or not. Then your child will move on to another stage of their development and you'll forget these considerations...
Then the baby will start to crawl, grow, gain weight... Because they now meet certain needs on their own, because they're heavy, because they want to discover their immediate environment themselves, we'll carry them a little less, on the hip, on the back.
They may be 6 months or 1 year old, it depends on the child.
Until what age to carry in baby wrap and baby carrier: 3 years, 4 years, 5 years?
The truth is that everything will depend on your babywearing method and your child's needs. Some structured baby carriers allow you to carry toddlers, others don't but can help out for occasional use. For baby wraps it's the same, some woven wraps can carry children over 3 years old but it won't necessarily be the most comfortable.
Then, perhaps at 3 years old, during a hike, a second birth, or because they're sick, you'll put your eldest back in the wrap by carrying them in front, or on the back, or on the hip. Then you'll rediscover babywearing for what it is: an act of love, a very practical act too.
