One of the nice things about using Apple devices, is that they receive major operating system updates for a longer period of time than smartphones and tablets running Android or Windows Phone. When buying an iPhone one can expect that it'll be served with the newest iOS for at least three or four years, as these charts by Michael Degusta and Fidlee nicely illustrate. While the majority of consumers purchase and upgrade smartphones alongside two-year contracts with their cell phone provider (unlike tablets), it's good to know that an iPhone will be usable and up-to-date even after a two year contract has run its course.
Of course older iPhones aren't capable of making use of every new feature an iOS version jump provides and in many cases the phones will feel slower because the new OS requires more performance, as this article by Andrew Cunningham at ars technica shows. The iPhone 4 is not able to run iOS 8, and it's a safe bet that iOS 8 will be the last major update that the iPhone 4S is going to receive, pointing to a four year update lifecycle for the iPhone 4S as well. The iPhone 5 and iPhone 5c are basically the same phone and their CPUs are very similar to the ones in the previous iPhone generations, which means that they should receive updates for at least another two years if Apple doesn't change iOS in a way that requires more processing power than the 5 and 5c can deliver without becoming slow to the point of uselessness.
When the iPhone 5s was released and subsequently reviewed by the incredibly smart folks at AnandTech, we found out just how powerful the A7 processor with its 64-bit architecture really is:
The A7 SoC is seriously impressive. Apple calls it a desktop-class SoC, but I'd rather refer to it as something capable of competing with the best Intel has to offer in this market. In many cases the A7's dual cores were competitive with Intel's recently announced Bay Trail SoC. Web browsing is ultimately where I noticed the A7's performance the most. As long as I was on a good internet connection, web pages just appeared after resolving DNS.
But the most interesting statement about the iPhone 5s's performance was made by Anand Lal Shimpi at the end of his review:
The A7's GPU performance is also insanely good - more than enough for anything you could possibly throw at the iPhone 5s today, and fast enough to help keep this device feeling quick for a while.
What Apple's silicon teams have been doing for these past couple of years has really started to pay off. From a CPU and GPU standpoint, the 5s is probably the most futureproof of any iPhone ever launched. As much as it pains me to use the word futureproof, if you are one of those people who likes to hold onto their device for a while - the 5s is as good a starting point as any.
John Gruber of Daring Fireball pointed out that the iPad Air with its A7 SoC was faster than a 2010 MacBook Air in many benchmarks, pointing out the desktop-class performance that the iPad Air, the iPad mini with Retina Display, and the iPhone 5s offer.
Early benchmarks of the newly announced iPhone 6 and iPhone 6 Plus suggest that Apple has once again managed to significantly improve the system performance of the A8 over the A7. However, these gains are similar to the past year-over-year CPU/GPU upgrades from Apple and not the kind of jump we saw when Apple moved from the 32-bit architecture of the A6 to the 64-bit architecture of the A7. While there are other significant internal differences between the iPhone 5s and the iPhone 6, like the improved GPU and the NFC hardware for Pay, the 64-bit architecture, the fact that the iPhone 5s and the iPhone 6 have the same amount of RAM (1 GB), and the Touch ID technology make these phone very similar in most other respects.
I'm sure the next versions of iOS will introduce features that require a lot of processing power and it probably won't be long before we see apps and games that take full advantage of the CPU/GPU in 64-bit iOS devices.
Still, I wonder if the shift to the 64-bit architecture might mean that in four years, when iOS 11 is released, the negative performance impact on the iPhone 5s will be comparatively lower than the impact iOS 8 presently has on the iPhone 4S, possibly making the iPhone 5s and the iPhone 6 and 6 Plus the first iPhones with an even longer lifecycle than the previous generations, more in line with what we've come to expect from OS X updates, where a MacBook Pro from 2007 will still be able run OS X Yosemite once it's released.
My 2008 pre-unibody MacBook Pro, that I keep around as a backup machine, is still perfectly up-to-date and usable. I really wouldn't mind being able to use an iPhone 6 for longer than the three years I've been using my iPhone 4S, even though I know that Apple will surely release something new and exciting next year, and the year after that, and the year after that …