How Low Do You Let Your Memory Get?

I reboot my phone perhaps once every couple weeks. No task killer since the first week. The phone is faster now than it was when I got it. Granted I'm running LPP over Blur, but there's almost never lag, etc.

If you are actually having a problem with apps running (not merely residing in memory) then a program like Watchdog is better, as you can still kill the programs, and it's actually watching for code that is using compute cycles rather than being left in memory (the latter is intended behavior).
 
I'll worry about how much memory I have left as soon as I ever have a problem - until then, I'll let Android worry about it. So far, after 4+ months, it's not been an issue.