What do you mean, 'let android' do it's thing? These apps are killing battery life.
I assure you that unless you have a rogue junk app that won't properly sleep because its poorly coded, none of those apps are drawing CPU/RAM and battery.
People forget that "free memory" is actually "unused memory"
The more apps pre-loaded into memory, the faster those apps pull up when you actually want to use them in the foreground, actually SAVING battery because RAM is so much faster than ROM or microSD.
There is no penalty for having multiple apps in memory.
However, if you get a taskkiller and start OCD killing them off, you'll watch your battery life go DOWN.
Why?
A) You're obsessively going to the taskkiller all the time, which uses battery and is fairly CPU intensive on its own because its monitoring so many aspects of the system. Checking taskkiller every five minutes will use a lot of power for the display as well.
B) Apps that you're killing will probably repopulate on their own, from ROM or MicroSD, which requires a lot more CPU and battery than if they were sitting idle in RAM
C) Killing system processes will likely destabilize your system and potentially cause a slew of "child" processes to clear and reload, draining a TON of power in the process.
Bottom line, i've NEVER used a taskkiller on my Droid Incredible and i'm averaging 20 hours between charges with fairly heavy usage. 50 emails a day via gmail push, a bunch of calls, couple hours of web surfing and music and occassional GPS / navigation use.
Heck, i finished fully charging the phone last night at 8pm. My uptime is 44 hrs and my awake time is 5 hrs and i'm sitting at 85% battery at almost noon the next day.