PENKO
Well, my FCOM's SOP section is taken over and ammended by my airline, so I could not really comment on what goes on in other airlines. All I can say is that my version does not mention switching them off.
So why switch them off? I say again, how do you monitor flight progress in the cruise? The map is synthetic; a VOR is real.
What I meant is that by switching the pointers off after TO I subsequently have to make a conscious effort to switch them back on in the correct way during the approach. I will then have a fresh mental picture of what is pointing to where.
There is no "correct way" - every approach is different and you monitor VOR or ADF as required by the a/c position on the STAR or approach. And what if you forget to make that conscious effort due to tiredness?
Your "mental picture" should last the whole flight, not just departure and arrival.