Holy crap, are you kidding?
8.1 can boot within seconds, if you have an SSD and a UEFI motherboard. The limiting factor here is old hardware- one cannot simply make older hardware move faster. If you want that boot time you MUST upgrade to an SSD, it MUST be partitioned with GPT, and your motherboard MUST support UEFI. These are the things that were created to improve boot time (among other things), they're here, go get them.
So boot time has already been solved by 8, what about performance? My 1GB of memory, 800Mhz CPU device (which is BELOW 8's minimum spec requirement) runs 8.1 very fast- much faster than Vista or 7 because of the performance optimizations and lower memory usage. So 8.1 is the lightest, fastest Windows since XP SP3 (also infinitely more stable and less prone to slowing down)- what exactly hasn't been optimized here?
Other things of note- sleeping a hdd doesn't prolong it's life, it just might save electricity (if that's your goal, get an SSD). The "thrashing" of an HDD happens for a few hours after the initial install of Windows while it takes care of things in the background. Otherwise hdd is accessed for caching and library purposes while you're using Windows and if you want to get rid of that you must also get rid of speedy boot times and general performance...