App killers DON'T help with battery power.

I'll add a bit more info on memory managment.

By default Android will keep the last used applications loaded into it's memory.  It requires less power to keep them in the memory than it does to kill them and load them later on. (booting an app requires the CPU, which happens to drain the battery VERY quickly)
When for some reason it needs to load a new app and free memory for that, it'll kill selectively.  The ones that are most likely to be used again are kept in the memory, and those that aren't needed are killed.

How does Android determine which ones to kill and which ones to keep?  Easy.  

The phone logs just about everything.  Which apps you use, how often you use them, which apps are used by the system, when certain apps will poll for new data (like the mail app polling it's server), etc.
It then uses all that information to determine the memory and power managment, so that it needs to use the CPU less and has the necessary apps already loaded into the memory when you use the phone.  
It takes a few days for the OS to log sufficient information and adjust itself accordingly, which explains why the first few days after a factory reset or a major OS update are always tough.  

All this can only happen properly if Android gets accurate data.  Using a taskkiller will only confuse the OS and will kill apps that would have been better off if left alone.  Yes, you'll save some energy by not having all these tasks loaded, but the extra CPU usage to boot them again easily outweighs that.

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On  a more personal note :

The first app I installed on my Desire (my first smartphone) was Advanced Task Killer (otherwise known as ATK).  I did that because many people told me that it was absolutely necessary if I wanted to have any battery life at all.  
After 2 weeks I had around 50 hours of battery life and was happy about that.

I then read a post about taskkillers and decided to remove it as a test (although I was very skeptical).  
The first 2 days I had no battery life to speak of, but afterwards I noticed an improvement in speed (because the right apps were always loaded) and saw my battery life increase to 55-60 hours.  

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All in all I agree with Sakai4eva.  
There IS a use for taskkillers, but only if you have a real problem with a certain app. 
Then again if you do have a bad app, you'd need to identify it first as the cause of your problems.  And if you do know that, you might as well remove or disable it and look for a replacement that works properly.

No real need to close it.  If you just exit it, it'll use less power than if you were to close it completely and open it again later on.  But yes, that will indeed take you back to the last page you used.

What you could do is either go to the home page just before you close the browser, or make a shortcut to your homepage on the homescreen and use that to lauch it.

Interesting info about App Killers.  I was running one that kills apps everytime the screen turns off.  It's fine until it kills something needed by mistake and the phone goes loopy.  I've turned it off and will see how it copes for a few weeks.  Battery life will be interesting.  The HTC Desire can be a hungry beast

Thanks.  I'll grin and bear it and wait for it to settle down again.  Is it wise to allow the battery to run down rather than charging it from half full?  I can charge it whilst at work but not sure if this is a good idea or not.

I was interested in the battery conditioning info but I've had my phone about 6 weeks so missed the boat I expect
 

It's now been just over a week since I read this thread and uninstalled my app killer.
At first ( the first two or three days) the battery life was dire.
Then it began to last longer, and I'm now on about 30% after a very heavy day call and text wise.
I would say it is much better WITHOUT the app killer!


Thanks.

Rags.

Interesting info about App Killers.  I was running one that kills apps everytime the screen turns off.

Thank you so much for this valuable information. Very useful.

Thanks for the thread sakai4eva. After reading up a little about how Android works after reading your OP, I uninstalled my apkiller and will not be reinstalling it.
I find the phone works just fine without an apkiller and I don't find the battery any better or worse, but the way Android handles memory seems much more logical than killing apps (that may need reloading) just because I didn't understand how the memory is handled.
The way I understand it, the memory needs power whether in use or not, frequently used apps will be readied in the memory making for faster load times under Android (a bit like superfetch in Win7), when Android starts running short of memory it simply does what your apkiller does anyway by emptying memory, also the apkiller is using resources too.
I'm actually quite tempted by Linux for my PC now I see how efficient it is.