MRB206: thanks for the cautionary word on the Holo Launcher consuming resources. I cannot say I encounter an issue there, in part because I don't monitor it, and haven't had a need to look at RAM consumption... Maybe it is one of your widgets.
But then, as a defensive measure, about every other day or third day, the phone is shutdown and restarted. That is a good suggestion for anyone.
For as much as people say manual memory / cache / task management is not a necessity in Android, I have a different experience.
You are most correct, it is a wide array of widgets and apps that may have hidden issues with memory management that are probably at root cause.
I also have no issue using 1Tap Cache Cleaner and Advanced Task Killer Free to make sure the caches are purged every now and then, and that respectfully, programs that don't move themselves to the microSD card get a little help from a friend.