From attending the odd club and exhibitions etc , I'd say the demographic that's now most prevalent seems to be 40+ , with minorities in the 60s. This is possibly due to the cost of railway modelling these days.
I'm the same age as Noel , but I'd didn't start haunting railways till about 73 , and as I lived in the country and my dad was car mad , we rarely came in contact with railways before I started traveling on them myself. I do remember an early trip to Waterford good shed ( the new one ) when H vans etc were in common use. ( and watching the shunting ) , but in reality all my detailed recollections were from the start of the super train era and while the sidings were full of laid up vans , the main trains were block or unit trains.
Personally , I prefer the immediate post Black and Tan period, the era of 1975+ freight modernisation very interesting , primarily because you had an explosion of interesting single purpose freight wagons . Equally that era began to be seriously chronicled by photographers an issue that bedevils previous eras in Irish railway history. My only regret was , that life pressures , meant I didnt run round the country in the late 90s , with my first digital camera , before all of it was destroyed from 2005 onwards.
I do mourn the current generation of young people who will have little or no variety to model, can't see the attraction in the post 2010 scene personally at all.