I didn't follow any training plans to get up to the half marathon distance. Once I'd finished the C25K plan I decided to see what 10K felt like and it was ok... did a few of those and then tried 15K. At that point I figured I could do a half and entered one. Although I didn't follow a plan I do keep an eye on my GPS watch to see what pace I'm doing - if I'm planning a long run I'll hold back the pace from what I know I can run so I don't tire myself out.

I think training plans depend a lot on what you're wanting to do - I just wanted to complete the distance; I could probably do it faster with a proper training plan but I've found running without worrying about time (too much) to be enjoyable (and I have still got respectable results for my age).

I made a 17km long ago without issues (only local slowdowns) but my body was different, hence my question.

Thanks for the links.