My perception of the ages is mostly based on the look and the actions (such as the Elder constantly slouching and indicating back pain). They don't run smoothly together, particularly with the older ages.
Babies: 0 - 1 1/2
Toddler: 2 - 3-ish
Children: 6 - 10
Teen: 14 - 17
Young Adult: 19 - 25
Adult: 50 - 65
Elder: 80 in ill health until they croak.
For me the Adult stage, with all the sags and wrinkles looks like late middle age. in the upper stage of that group would be the horrors of menopause. Hot flashes! Broken sleep! crankyness! And too many other symptoms of awfulness to name! (Yeah, definitely not fun times).
I feel like we need to change the Adult stage to Middle Age and make Adult stage more like 35 - 50 so they can all have mid life crises and buy sports cars, have affairs with younger people, get divorced and get younger trophy wives/husbands. basically a big stereotype, but it could be interesting.