NEW YORK — Ironclad, two-year subsidized cellular contracts are rapidly becoming a thing of the past tempting you to upgrade your smartphone more frequently.

That temptation has been on the mind of iPhone owners ever since Apple CEO Tim Cook announced the 6S and 6S Plus, even people who sprung for the 6 or 6 Plus models within the last year.

Trading up this soon is certainly by no means necessary, but those of you who do will be happy that you did. Apple’s marketing spiel, heard in one of those chief design officer Jony Ive promotional videos, is that these are the most advanced iPhones ever created, but there is truth behind the hype.

The odd-year “S” releases of the iPhone sometimes get a bad rap, with people thinking such models are only marginally better.

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