Perhaps it's just my own background that pushes me this way - but as soon as my deployment was growing ot eat up anything over about 60% of my available memory,

Perhaps it's just my own background that pushes me this way - but as soon as my deployment was growing ot eat up anything over about 60% of my available memory, I'd be looking at deploying more. Your high water mark for spinning up more nodes and/or upgrading shouldn't be your maximum physical ram capacity - that's just nuts.