Cool it sounds like you're experienced!Yay Cubase! Me too! It's mostly sample libraries that eat RAM. Especially orchestral ones. You're loading up a bit of every sample of every instrument of every at every dynamic layer, different articulations, etc.
I personally work in a fairly efficient way so my template uses around 26gb of RAM total, but I use pretty lightweight orchestral libraries without so many mic positions, round robins, etc. But I wanted to have room for growth too so I got 64gb. I know some people who use 128gb because they are RIDICULOUSLY detail oriented about orchestral stuff and want to use the biggest and best libraries all loaded into their templates at all times.
I've just started and I'm only recording the guitar and base at this point, and no Cubase amps, I'm using a Two Notes Torpedo Live which has mic simulator. And I have a midi drum track.
But there is still so much I don't have have a clue how to use, the RAM issue will probably show itself later on.
Cubase is so much fun though! I'm coming from using a Tascam porta studio so it feels like the possibilities are endless with Cubase =)