I've figured out a couple of alternative 'circuits' to walk - the short one is about 8km (5 miles) by my rough reckoning - the long one maybe 13km (8 miles)...
my son has come with me twice on the long one, IIRC.
It's amazing how much it clears the mind - alternatively, how many ideas occur to me during the journey.
I will need to learn how to use the voice note-taker on my MuVo TX... so I can capture them for later processing and hopefully implementation.
One idea I did retain without hi-tech help, was that I could use GPS and my PDA (under battery repair presently) to plot the course of the walks and measure pretty much exact distance... and a coupla other things which I ain't disclosing here :)