Greetings fellow Z'er.
I wouldn't hold out much hope for the Nokiasoft. The Nokias of old managed their impressive battery life by having very low power CPUs (we're talking number crunching power, not just battery sucking power here). They could do this because they were running a very efficient OS, Symbian.
Symbian was built from the ground up in the days when mobile devices just didn't have huge powerful CPUs. Android, WinMo and IOS aren't. They're all stripped down version of big OS's.
In the world of mobile devices there are always compromises. With Symbian the compromises were almost exclusively made in favour of low power consumption, because the power just wasn't there at the time to be used! The newer OS's had the CPU power, and have used it (programmers always use everything available to them, plus a bit more). Occasionally they have actually given us something useful too.. Which we got used to, and liked.
I doubt we're going to see 3 days phones for a while, not until the "dual core" willy waving is finished and everyone calms down to let the battery technology catch up!
You can actually get quite a few days out of a DZ, I discovered this (thanks to the excessive EU data roaming charges) when I went abroad... Data off, wifi off, bluetooth off, and remember to switch into flight mode if you go into an area of no coverage (stops the radio cranking up to full power and screaming the cell equivalent of "HELLO?" all the time!). It also helps that you tend to keep phone calls short due to the roaming charges too. Best I saw was from fully charged at 6am to 92% at 9pm!
So if you just use your smartphone as a phone, everything is good... Now I just want to use the "smart" part please!