I am 29 and currently in my first year in halls, to be honest it has been more bearable than i first thought it would be. My flatmates are generally pretty good, 5 girls and 2 boys, 19-20 years old, we all get on pretty well, i just have to endure the banter of being called gramps, but it is all good hearted.
The things that annoy me on the other hand are: constant fire alarms, 5 times in one night at its worse, other people in the halls, screaming and shouting into the night, when you have an exam the next day. the walls are paper thin so you end hear everything, and i mean everything, and a few of my flats are quite lazy when it comes to cleaning their cutlery etc up.
I am glad i have experienced it, but i am longing to be in house for next year, hopefully with other mature, masters, phd students.