Re: what are alternatives to android?
Without more details, it's hard to diagnose what may be going on in your particular phone. If you just don't like the Android environment, then I hope you find something more suitable to your needs. If you want to explore and see if you actually have a problem that can be solved, then read this article.
http://m.androidcentral.com/ram-what-it-how-its-used-and-why-you-shouldnt-care
Basically, ram uses the same amount of power whether it's holding data or not and Android is designed to take advantage of this. By keeping apps dormant in ram, it's not using any extra power and saves battery life by not using extra CPU power to initialize it every time you open your more common apps. Having ram close to full is a good thing!
Battery managers, task killers, memory optimizers, et al are counter productive because they try to fight the design of how Android manages ram. When they kill dormant "unused" apps, the OS will automatically reload it or another app in the background to fill the empty ram. Every time an app is loaded in the background, it'll use extra battery life in doing so. This is hard set in the OS and can't be changed without rooting and changing things at the system level that may be beyond your skill level. Memory managing apps actually decrease your battery life by killing apps, and current versions of Android are pretty good at managing background apps on their own.
That alone may or may not be the reason you're only getting 4 hours battery life. My battery can last ask day with light usage, or I can drain it in a few hours with some heavy gaming. So usage can play a huge role in life too.
Sync'ing can also play a big role. Yes, apps can lay dormant in the background, but you'd be surprised how many are designed to do work. Pretty much any online messaging service, email apps, weather apps, and a myriad of other apps may all be setup to check for messages and updates from their respective servers even though you're not actively using them. Many times they will have options about when and how often to sync.
Then of course the battery itself could just be defective or going bad. Age would be one factor, but draining a battery completely and/or leaving it plugged in after it's fully charged can both kill a battery prematurely. If you've done everything you can to decrease consumption (limiting app sync, lowering your phone usage, removing Battery Doctor, using Wi-Fi whenever possible, etc) and you still get very little time on a charge, then it's most likely the battery is on its way out. If it's removable, check to see if it's puffed up any. Lay it on a flat surface and spin it. If it continues to spin on its own, then it's swollen even if not immediately visible, and the damage is already done. Replacing it and being mindful of how you charge it should give you more life. If you are a heavy user, there may be larger battery options for your phone do you get more life on a charge at the expense of some added weight and size. Most people suggest charging it once you get around 40%. Letting it drop very low or leaving it fully charged cause a chemical reaction that lowers capacity. That's why new phones and batteries are shipped with a partial, "storage" charge.
Hopefully this helps you out.