All of these weaknesses being cited were 'after the fact', only becoming an issue once the next generation was out or on the verge of releasing. Upon release, every new model was the reincarnation of Jesus in iPad form and will be a good 'future-proof' model. Just read any review for any of these when they first came out. They were all 'Best iPad EVER'.
iPad 3 performance was good at release and for a few years though iOS5 & iOS6. iOS7 finally took its toll on performance, but it still was OK, and that wasn't released until the Air was out, 2 generations later. There was no overheating issues. I had one, it never overheated. The A5X with its quad core GPU was incredibly impressive and there was high praised for the Retina display.
iPad Air was highly praised for the revised form factor, greatly reduced heft, and lightning fast A7 processor (that was 2x faster CPU & GPU than the A6X). A year ago, having an A7 means you had a 64bit processor and were prepared for the future in terms of CPU power. Today is somehow is a terrible tablet because Safari reloads tabs.
As it stands today, the Air 2 is the best iPad made. It is a great device and I would really like one. I believe it will have a nice usable lifecycle, but those same claims were made for every iPad before, yet we see certain models condemned or praised for one reason or another.
Fast forward to a year from now and I guarantee there will be some type of complaints about the Air 2 next year. The issues we're seeing because its too thin, vibration, distortion, short battery life will be raised. The Air 2 looks the same as the Air 1 with no decrease in weight. Performance wise, people will complain the A8 was only a minor variation of the A7 so single core processing isn't much improved at all. The 40% increase of generation to generation CPU performance is the 2nd lowest ever for iPads (2nd gen & 3rd gen were about the same) and the smallest for a next gen A* processor we've seen. Every new A* processor (A4 -> A5 -> A6 -> A7) was was 2x CPU improvement except for this one.
The Air 3 will be awesome because the A9X is a complete redesign of the mobile processors that vastly improve both single and multi core performances. With updated design language, it will make the old Air 1 and Air 2 look out of date. The chamfered edges made the Air 2 less comfortable to hold and the new edge glass like the iPhone 6 make the Air 3 much better to use.
Ok, that was long winded, my point is that everyone always thinks the newest iPad is the best model that will last forever. And they're correct until the next model comes out, then that model will have something 'we need for the future'. Longevity is more dependent on Apple's roadmap than it is about a certain hardware specification.