Personally I think I'd just stick with the automated cleanup, since so far that has always been 'good enough' for me in the past.
My thoughts exactly. A garbage collector is in a better position to know exactly when to delete a dereferenced object from mem than we do. In fact it already does this - calling FlushMem doesn't instantly restore our lost memory - it's completely up to the discretion of the gc. So calling FlushMem manually in an automated system doesn't make any difference.
I could understand if the automated system was switch-offable though.