Not having had mine fail nor the opportunity to examine numerous examples, the only information I have is the reports here on this forum and what I've gathered by talking to mechanics who have worked on these engines.
There are a great many more Navaras than we have members in this forum, so what we have here is just a small sample. While it's true that people are more likely to visit a forum such as this if they have a problem (compared to the chance of visiting if there's nothing wrong - if there's no reason to look for info, why look at all) I don't think what we see here is truly representative of the car as a whole. This means that sometimes we'll see a trend that we've correctly identified right across the range - for example, vac hoses or solenoids, weak front diffs) and other times we won't.
That was the whole point of this thread - to try and gather information and see if there IS a specific area that causes problems. Judging from the feedback received, those tensioners look like an issue, as do the choice of oil filter. In reality it's anecdotal evidence - which can provide somewhat of a case, and give people a guide as to where to look or things they might do to reduce risks.
If I was asked specifically what I'd do to reduce risks - based on what I've learned in this thread - I'd say "always use a genuine filter and regularly change your oil with a good quality oil".
