"As far as I'm concerned anyone still pulling down hard - or hell just pulling down at all - at 50+ has sucked it up and gotten their addictions prioritized right. Getting on it when you're a teen or early twenty-something is one thing; it's an entirely different story "re-dedicating" yourself to it decade after decade as you grow older. I've found that somewhere early in each decade my body has changed a bit and I have to adjust and adapt for about a year and then cruise for nine until the next one. I'd love to see the decadal attrition stats for climbing. Then or now you can bet it's a steep drop-off.  
  
What would also be interesting is to see the attrition stats as a percentage for each year from the day folks climb the first time - how many anniverseries do they survive as a "climber". Back in the day when all there only was trad, placing gear was a fairly stout threshold / barrier that acted as a relatively efficient filter - most folks decided pretty quick whether they were in or out. Today, though, you can linger on plastic and bolts indefinitely without really progressing as no such threshold exists in sport climbing which has a low barrier to entry. And that's probably matched by a heavy tidal flow of casual users through gyms so the anniversery clock should probably be started the day they buy shoes, harness, and a membership rather then when they tried it for a day with rental gear. "