Hi Phil. I wondered where you were!
Your ballbuster was an impressive result - especially for a trackie! I had considered riding it as it was 2 weeks after my autumn target of the Chilham duathlon and I figures I could hold some form, but instead, I literally had my balls busted 4 days beforehand! 
I was 3rd in the Thanet off road duathlon last year and am doing that again in 9 days time. I was also planning to do Maidstone duathlon in March. I was 5th last year and was looking for a similar result this year. However as CD noted, a duathlon is probably as good as a 20m progressive run if all legs are controlled. I know that I won't do this. In last years event the 9.5k opening run was run within seconds of my 10k pb pace, I died a bit on the bike (lack of training) and forced myself round the final run. An all out effort from the gun and I can't imagne this year I would be able to control myself any better.
I think it worked as a god training day and also reignited the TT spark a bit - I managed a low 23min evening 10 and a 1.1.29m TT in the summer - and I also improved to win and get some reasonable results in a few other duathlons throughout the summer. However it was hard, trying to short distance speed in both running and cycling.
Although I was cycling strongly in the autumn, I hurt my knee about 1 month ago and it keeps coming back when I ride for more than 90mins. To be honest, since 'winning' this thread, I have started that rather than trying to split my eggs between a few baskets, I would be better on focusing on the running and just ride occassionally to break it up a bit.
That said when I refocus on duathlons, a 10 - 12m Sunday run followed by 45m on the bike plus 2xturbo session in the week will be my bike training with a tempo, 1hr hilly and shorter interval run session as well. But it does seem to mean that every day is a training day.