India, Oct. 16 -- Most of us judge a new phone in its first week. Apps open quickly, scrolling is silky and everything feels sorted. The real test comes in year three, when a chat app takes a beat longer to launch and the camera needs a moment before it is ready. The OnePlus N6x, priced at 17,499 during the Amazon Great India Festival, is built around that worry. Its headline feature is a 48-month Fluency Certification, which OnePlus positions as a promise about everyday usability over four years rather than a launch-day performance number. For anyone who keeps a handset until it truly gives up, the OnePlus N6x 48-month smoothness claim deserves a proper look, so here is what it covers and what comes with it.

The highlight of the OnePlus...