Flying across the Oggin or the Sahara you are a bit short of navaids, so it follows that you <have to> trust the map.
Once you have done it for a few hours at a time it is quite compelling. Having said that, going into somewhere like Moscow, map shift occurs quite often and can present a problem. Cross checking with navaids is always good - but if you have just cross checked with the navaid that has given the dodgy update, then you are still none the wiser!
How do you tell which of the navaids is dodgy, unless you cross check with three?