"Capt obvious here: Lengthening the battery life is good but does nothing to help the problem of batteries holding less charge over time. In the end a battery replacement is still necessary if you want to use the same phone for more than 2 years."
That's just it, no you don't. Because my S3 barely made it through a day when it was brand new, it needed a new battery the 2nd year, before my contract with it was even over, the loss of half an hour meant I wasn't even getting through the work day, let alone having any charge in the evening.
Because the S5 comfortably lasted a day and half or so, even losing a couple hours hasn't been an issue, its over 4 years old now and my wife is using it; on the original battery, and it's still fine because it still easily lasts the full day and beyond. So, by lasting longer its directly address the need for replacement.
And the S7 is even better.
"I personally keep my phones until they break..."
Sure. Me too at least if you count 'hand me downs' within the family. But its at the point now, where I might have to replace one battery one time after 4-5 years to get another 4-5 years, that's easily the device life.
"having user replaceable batteries is something I value a lot."
And that's just it, why? As long as its not a ridiculous project to replace, then it it's an hour of your time the one or two times you replace it, or it costs $10-15 have the guy you bought it from replace it for you while you wait in 15 minutes.
Why should you put a lot of value on being able to swap a battery? If its something you'll do once every 4 years and costs $10-15 bucks... its just not that big of a deal.
Sure if you run through multiple batteries a day, that's one thing. (But there are external power packs and battery-cases that probably would suit you better if that's your need.)
But if you are demanding user replaceable batteries and dramatically limitting your choice of phones, just to save $10 four years from now? That doesn't really make a ton of sense.