I generally have zero perspective on myself, in dreams. I assume I am adult size, because of my relative size to everyday objects like houses and their contents. But, I don’t know that I have an age, generally. There are never any mirrors in my dreams; I might not even be me/myself, I may just be the subject/observer of the dream.
Also, while dreaming I can sort of learn things from printed materials, if the dream scenario calls for it, but I cannot read words. That’s actually my dream tell, if I can look at letters and read them, it’s not a dream. If things get weird to work around the reading thing, then it’s a dream.
As for my internal age… I’ve never felt my own age, but it’s closer now than it’s ever been before. Maybe I’ve always been 43 in my mind. Actually that would kind of explain why I was a weird child who was super impatient to become a grownup.