I'm certainly no mechanic, but what was explained to me was that with age and mileage the 5w30 that was recommended when new will seep through the (piston seals?) and get burned, so switching to the thicker 10w40 oil prevents that to a large extent.

The nikasil issues were nearly 20 years ago, so any engine's either been fixed or replaced, I wouldn't be concerned about it in 2016 to be honest.

I too am a firm believer of frequent oil changes and changed mine every 5-6k no matter the age of the car I had, if you've no trouble with 5w30 between services then stick with it, if not maybe get a 2nd opinion from the likes of Motor Confidence or Super4 re:10w40 and I'm sure you'll have a reliable answer