Brilliant thread and thanks to Giles for taking the time to point out stuff.
This leads me to a question about retaining focus on longer journeys. I often tell myself 'heads up', i.e. Keep observing as my focus reduces with time, but the reality is sometimes you just need to push on. Any tips?
I guess there's no magic bullet answer to this. Ultimately being 'bike fit' will see you being able to sit in the saddle for longer both physically and mentally. Because I spend my working day on a bike my 'bike fitness' is good so I tend not to suffer from aches and pains or concentration loss. My wife on the other hand only goes pillion once in a while, so when we hit the summer two week tour she gets absolutely exhausted within a few days because she's not 'bike fit'.
Noise is a big factor to concentration levels and tiredness. A quiet lid and effective earplugs will really help as of course will decent bike kit that is comfortable and cool / warm. Make sure it's all 'done up' properly. Nothing like an itchy sock or a draught down your neck to keep distracting you for hours on end! On that .... I always have a little mental check list before i set off. Another real distraction to your concentration is if you've left a pocket open and now you're constantly thinking about what was in it or some scenario like that. Spending just two minutes patting yourself down, double checking panniers locks, wallets, keys ... you name it, means that when you set off, mentally you've not got a distracting nagging doubt nibbling the back of your mind.
And yes, the others are quite correct about having a break. In the Rapid training days the students always ride really well after lunch where they've had a break, had time to process all that info and start again fresh.
Even Johno managed to improve after lunch ...