I'm very comfortable with my advancing years and if someone asks my age, I don't suffer from any embarrassment or indignation about answering truthfully - by the way I'm 47 this year.
I believe it's a state of mind, if you're comfortable in your own skin, I believe you're comfortable with people knowing how old you are. I'm quite lucky with my gene pool; my mum and dad both looked younger than their years and I'm often mistaken for someone 5-8 years younger.
I've often wondered what I'll look like when I'm 60 or 70 and would still have no hesitation letting people know my real age.
I don't mind if friends know, but the other day on the bus my 8yr old called form the back of the bus to me at the front "You're 36 aren't you mum" and it gave me pause for thought lol I didn't want all the people on the bus knowing. Weird!
I also had no idea how old my father was until his 80th birthday! He would never answer when I asked him.