Let me give you an example.

This year FRA Champs Pendle, happens to be an Open race and also the Lancs Fell Champs.

2012
U12 Race is 3km Open, Lancs Champs and FRA Champs age on 1st Jan. Very straight forward as we all work to the same date.

Under the new rules his U12 Race age on day still is 3K. The only real difference it makes to David at Pendle is the calculation, that some current U10s with DOB between Jan 1st and race day will become U12s.

When I come along with my Lancs Champs, I will have to adopt those age groups. I can live with that as long as David allows me to piggy-back Pendle as other than those with birthdays around the first week of April, birthdays will be consistent each year. So Lancs Champs races will still be a 2 year progression.
My problem comes if David says he can't host for me and I have to look for another race - perhaps Darwen in August as we are not awash with Fell races for juniors that I can use as an option.
Then I could have runners with birthdays in that April - August period staying in the same age category for 3 years.

That is further complicated when Duncan approaches Pendle, as David has to make the race accommodate the FRA Champs 1st Jan requirements.

So when David permits this existing race how does he do it? It will be really interesting to see the paperwork for the RO and the entry forms.

I think when you start to get your heads around that, the penny may drop.