I've had a 2013 Moto X that still performs perfectly fine. Only problem is that the battery has degraded but that's going to happen with any 2 year old phone. I've been updated from Jellybean to Kitkat and Lollipop. Can't really complain much. Definitely got my 2 years worth out of it.
Any flagship device you buy now is probably going to last you two years. Especially with current feature sets. I must be the only person on this forums that couldn't care less about software updates. If the phone isn't how I want it out of the box, I don't buy it. I'm not going to rely on an update that may or may not come to change things.
iOS is nice in the sense that you'll probably get updates for as long as you're likely to use the device (2-3 years). The issue with apple is that the updates will often degrade performance to the level that after the 2nd or 3rd update, most people will be clamoring for a new device. People can argue whether or not apple does this intentionally. You'll also get the people that say their iPhone 4S or iPad 2 performs better on iOS 9 than it did on iOS 4/5. All anecdotal of course.
Any flagship device you buy now is probably going to last you two years. Especially with current feature sets. I must be the only person on this forums that couldn't care less about software updates. If the phone isn't how I want it out of the box, I don't buy it. I'm not going to rely on an update that may or may not come to change things.
iOS is nice in the sense that you'll probably get updates for as long as you're likely to use the device (2-3 years). The issue with apple is that the updates will often degrade performance to the level that after the 2nd or 3rd update, most people will be clamoring for a new device. People can argue whether or not apple does this intentionally. You'll also get the people that say their iPhone 4S or iPad 2 performs better on iOS 9 than it did on iOS 4/5. All anecdotal of course.