742,
If I understand you correctly, you are asking how long an average student will spend learning navigation on a PPL course?
In that case, I don't know about an average student, but I can tell you what I used to get my PPL students to do.
I used to work on the general principle that I wanted to see a student do something twice before I'd let him do it himself. So we would do two dual navigation trips before I'd let my student do his first and second solo navigation (which would be repeats of the two dual trips). Then we would do two dual land-aways before I would let the student do first of all a solo land-away, followed by his qualifying cross country.
So that makes a total minimum of 8 trips, 4 dual (including two land-aways), and 4 solo (including a land-away followed by the QXC).
As well as that, there would be further dual trips covering unplanned diversions (at least one flight) and radio navigation (at least one flight). And all of this would be revised prior to skills test.
That's an absolute minimum. It's quite possible that someone wouldn't reach the required standard on an exercise (i.e. a standard where I'd be happy to allow the student to repeat the trip solo), in which case it would either be repeated, or I'd find another different route to consolodate whichever aspects needed more work.
Bear in mind, though, that this was my own personal interpretation of my school's standard syllabus. It's entirely possible (probably, even) that other schools and other instructors do things differently.
As others say, though, this is only the beginning. I now teach the CPL course, which includes a lot of visual navigation, and I am still learning new techniques all the time. And we're just talking about visual navigation combined with ded reckoning - there's a whole other world of radio navigation which is only covered very briefly in the PPL syllabus, but which you could ask any instructor to spend as many or as few hours teaching you to a more advanced level.
FFF
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