Now that a few days have passed I have had more time to digest the race.
In general my training was very close to last years, even made a couple small adjustments to peak for just this race.
I think it was perhaps several factors working together:
1) Although I tend to stay in a heat training mode whenever possible we did have a slight tailwind, although hardly noticeable. This made the temps. effectively hotter even though it was only in the upper 60's and sunny.
2) Hydration perhaps a factor, due to not having to go until hours after the race despite drinking lots of fluid post race.
3) Went out harder than usual to stay with group. Pressed pace in miles 6-8 harder than usual. One of my goals was to run a “harder” effort for a half marathon. Perhaps I have already been running them at the right effort level early on in the races.
4) Comparing times the guy that beat me by 45 seconds this year was 60 seconds ahead of me last year. He ran slower, as did others that ran the year before. Conditions were just a bit warmer, hence slower times.
In retrospect if it had been a 12 mile race it would have been just the right effort to leave me in that “please let this end” mode over the last mile. I have another half in about 7 weeks, and a hilly 15 miler in 10 days so at least I will get another chance to run some more long ones soon.
Thanks for all the input.