On Mon, 4 May 2009 06:47:33 -0700 (PDT), MIG wrote:

(If people really had to leap out of trains to touch validators at
places like Earls Court it would hardly be healthy or safe. Would
they leave their luggage on the train? It would be too bonkers even
for TfL under the rules of Oyster.)

You wouldn't have to leap off the train - the intermediate validation
would only need to be done at a station where you were changing trains
anyway.

Essentially, I'm guessing (from the list of stations provided) that,
for example, the Z23456 time limit will be enough to travel Z6 - Z2,
but not (necessarily, perhaps in the event of delays) enough to travel
Z6 - Z2 - Z6. So at the interchange station in Z2 (where you "turn
back" and start heading outwards again), there would be a validator to
touch which would extend your time.