Do people tend to stick at 5 k runs once they hit that point or start training for 10 k?
Most people keep upping the distance til they settle into a nice routine that fits with their lifestyle. Of all the c25k groups we've run through our running club, I'd say the majority of graduates go on to regularly do half marathons.
This makes sense to me, as its a manageable distance that can easily be tackled on a couple of short runs plus one longer run a week.
A few graduates go on and stop at 10k but tbh, there's not much between a 10k and a half in terms of training commitments and the effort required.
But then there are lots of c25kers (me included) who find themselves doing marathons and ultras, and another bunch who stop altogether.
IME you can always tell the ones who will stop altogether, because they were the ones who would use any excuse to get out of a run during the course (it's raining, I'm tired, I'm due on my period etc). It's the ones who are mentally tough, not necessarily physically tough, who go on to succeed.
I'm particularly thinking of one lady on one of our c25k courses who must have been a size 22 or 24 when she started. Her first 5k took her more than 45 minutes - but she did it, and she always turned up and gave it her best shot. She went on to run half marathons (losing a fair bit of weight along the way) and ran a fairly impressive 2:05 in her last half. Now she's in training for a full marathon. But looking back at her c25k cohort, any outsider judging her on day 1 would've guessed she'd be the least likely marathon runner of them all 