At the risk of sounding like a clueless bufoon, can I ask why exactly it is frouned upon to climb on stones, is it a respect thing, or are we seriously saying that a barely 11 stone bloke will break or wear down a several tonne capstone or standing stone.
But it's not one 11 stone bloke, is it? Let's say the stones have been in situ for 3000 years, give or take. Let's imagine that someone clambers up, say, once a week on average. In the Victorian era whole parties used to clamber on the stones at once - see the old photos, so once a week is probably a fair average.
That's roughly 150000 'rubbings', plus the same amount of 11 stone+ stresses being placed on the stones and their contact points.