Dear Chris,
The title of your thread, in World.h 
#Running When You Want
You could run it on a timer
//void ForceGarbageCollection( bool bFullPurge = false ); //I use True
GetWorld()->ForceGarbageCollection(true);
#Crashes Solution → IsVallidLowLevel()
For actors that could be garage collected,
you can do this check
if(!Actor->IsValidLowLevel()) return; //dont try to access null or is-being-destroyed
Actor->DoStuff();
I find that catches a lot of what would otherwise be crashes when GC has just been forced
Rama