I'm never going back to android... Why should I have to buy a new phone to have the "privilege " of running the latest iteration with the latest updates because the scam artist manufacturers won't update the system because they want to force me to buy their latest phone...
Running iPhone 6 right now and have already gotten 2 superb OS updates and a number of security updates as well...
I'm never going back to the android ecosystem...
Buy phones with chipsets being well supported by Cyanogenmod and you'll have lots of OS updates for free for years to come. Pretty much means you need to buy Android phones with Qualcomm, Samsung/Exynos, Intel, or Nvidia processors. The "other" SoC manufacturers don't release the source code with their products which is required for other engineers to be able to make their own spins of the software for those devices.
What they're doing is illegal but since they're mostly in China there's nothing we can do because China be like "fuck following international laws".
Bottom line: avoid Mediatek, Rockchip, Allwinner, and Amlogic based devices for a good android experience.