I said:
Unless you're very good at predicting the future,...

Then you said:
Now it must be productive miles I'm logging, but I don't really know how
productive I've been until I see the score sheet, now do I?

That's what I meant about predicting the future.

If your average speed is going up, and you can be sure that it
will continue to do so, then of course it is wise to stay out
longer.

-Pat