Speak for yourself, bruh. The older the berry, the sweeter the juice XD. Cougars, milfs, I dig em. Not that I saw Cassandra as a cougar, and to be a milf, she's gotta be a mom, so.
I do tend to play inquisitors or characters in general by their mid thirties, late thirties, or early forties, but just because that's the age I consider a man in his prime. Not that my characters need to be in their prime, that's just how it turns out.
What you consider is unfortunately, false.
Scientifically, both human males and human females reach their physical peak anywhere from mid 20s to early thirties. So somewhere between 24 to 32 years old. If one take care of themselves really well or just have good genes or both, this can be extended up to their 40s.
As for reproductive fitness, both men and women start tapering off after the age of 40 with women tapering off far more drastically than men do.
However, intellectual capacity has no age limits. So if you want to be on your prime game for a long period of time, you have to be a pure spellcaster. The brain just has a better shelf life compared to other organs in the human body.
Its also why I call the Rogue class as the Young Folks class. You can only do the agile stealthy moves efficiently up to a certain age, after that you have to rely on technological enhancements, rigid care for the body and good genes.
Note that everything I have mentioned only apply to Humans, so it would be a different story altogether when it comes to Elves, Dwarves and Qunaris.
My Lavellan is 31 years old, so there's that...
How on Earth did you make a Lavellan in his 30s is beyond me since all the Elves I made looked very young ? Its hard to make old Elves or middle aged Elves.
No really. Fiona is supposed to be old. Ameridan is supposed to be really old. However, they don't really look old the way old Humans do. Its just an Elven thing I suspect.