I kind of view them as all ages. I’ll dress kids up fairly young when they first age up representing 5-8 then dress them older and change hair half way through their lifespan so they are 9-12.
Teens I do the same dressing them younger to kind of represent innocent 13-15 year old and then change them up halfway through to represent 16-18
Same with YA...only I imagine it to be 21-35(ish)
The adult 38-55
Elders I keep their hair their natural colour and then switch it out for grey towards the end of their life representing 65+