In wouldn't say the average age is around 25, I'd say more like 28-35.
My personal guess is 80% of the expat population is between 25 and 40. It makes sense because Dubai is not really a country where you would like to retire, so it attracts young people.
So I'm special here
;)
I'm nearly 50, but it is a very young population, I believe the average of females is less than 30, somewhere around 25. The average age of men is not much older. The healthcare here has not been very good unti lately and up until recently I believe expats were repatriated at 60.