To be honest, at the Cambridge one I'd say there were about 20 people there altogether. Very few of them looked under mid-20s. The rest must have been split pretty much 50/50 between the 25 - 35 and 35 - 45 years old age brackets. (This in a city very heavily populated by students and young professionals).
On the plus side it did mean there were plenty of people there to help newcomers; act as sponsors; take on a bit of service; etc.