In reply to Ramblin dave:
As a member of my local mountaineering club for many years, it's a problem that I've been aware of for a long time. We've got an active group of members involved in climbing, hillwalking and other outdoor activities, and we have a pretty good website and Facebook group.
Yet still we struggle to attract younger members. I don't think that collectively we're a particularly boring group of old farts, and the cost of club membership is low in relation to the benefits available (access to club huts, subsidised training, free lectures by top climbers etc etc)
The club has had a stable membership of over a hundred for at least the last decade, but the average age keeps creeping up.
I'd be really interested to hear from members of other clubs if they have been able to overcome this problem, and if so how.