I was taught (still teach) 6 minute marks as it eases the arithmetical workload on the student and, most importantly, gives the student a 6 minute cycle into which a cockpit routine can be put.
I think it's all too easy for an experienced pilot to dismiss the method, having since moved onto a technique that suits, but is a student going to have the capacity or experience you can draw on to sort out their pet method? I have been with students assigned to other instructors on navex's where the instructors' pet method has left the student thoroughly overloaded. They use the six minute marks and it all becomes a lot easier. Some of the alternative methods taught were quite good (and some not) and I could see myself using the better methods occasionally where circumstances dictate but surely it doesn't serve the stude in their basic navigation training if they're being overloaded doing the sums.
Anyway, why make it overly complicated?
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0 to 2000ft in 10 minutes