Gasax,
I meant roughly every 6 to 8 minutes find a feature on your route that you can use (I'll be passing 2 miles to the left of this town / 1 mile to the east of this reservoir etc.). If you choose 4 mins for a good fix, or leave it for 10 or 12 then thats fine. I didn't mean make marks every 8 minutes along the leg then force yourself to find something there.
You are flying the heading you have calculated and occasionally referencing that against your track made good.
I guess the most important time for using DR is when you are navving in 3km visibility, which is of course legal. Town hopping may be impractical because you may not be able to see the next waypoint. At times like these DR is the only way to nav (bar radio aid/GPS nav of course) and so surely it must be better to teach people the method that will work for all conditions that their licence allows?
One quick point - I guess there are two types of track crawling, for instance following the railway out of Redhill to Ashford. Dead easy, low workload etc. etc. The other type is the run your finger along the line and update your position every 15 seconds with the multitude of small towns you can see. This is easy enough if you are familiar with the area but constantly referencing the map can lead you very quickly into persuading yourself you are somewhere you're not, and makes your lookout now virtually non existent.