800MB free RAM yet home screen redraws? my lowest priority app-kill min-free level engages at 64MB.

if I have 800MB of free RAM as reported in OSMonitor, why is the garbage collecting Nova Launcher assets? I can't even.

BTW, I have noticed this behavior in Android for many years, across launchers, across phones. I don't think it ever really got fixed-- remedied perhaps; I think people just gave up fussing. From the user's perspective, nothing should be cleared from RAM unless RAM is needed.
This is a rather old question but Nova Launcher has an option to stop (most) redraws.
It can be found in Nova Settings &gt; Advanced (at the bottom of the list).
It reads:

Aggressive desktop
Persistence, caching, and preloading to reduce redraws. Comparable to Keep in Memory option of Android 2.x launchers.

It's not a good idea for phones with low RAM (&lt;=1GB), but if you have 800MB free (so, assumingly, your phone has 1.5 or 2GB), it should be just fine.
There should also be (persistent) next to the app name in Android Settings &gt; Developer options &gt; Process stats after changing that option.