Yep, morphs and texture size are the two big things.  I've done a few scenes with multiple characters who have been heavily morphed, and I've even gone so far as to remove the unused morphs and still the scenes have taken forever to load and to save.

I've been meaning to try and learn how to bake multiple morphs down into one character morph, I think this would save a lot of memory.  How would one do that?  Export the character as an obj and then re-import as a morph target?

I'm going to go try that right now and I'll let you know if this helps.