We can't know. You have not provided any detailed info about what assets, effects, functions, settings and so on are used.
If you have the 3d camera tracker applied, delete it. Once you've extracted your camera and position data, you don't need the effect sitting back there.
If you have the Warp Stabilizer effect applied, pre-render that layer to an intermediate codec, use the resulting video file in your project, and delete the layer with the Warp Stabilizer effect.
In both cases, I'd recommend saving your project incrementally or with a new file name or something in case you need to go back and adjust something.
I've got a camera (not 3d) moving through space with animated comps coming up at intervals. There is sound and music.
thanks for the tips!
Wait, when you say "memory use", what do you mean? When you were talking about project size, I was thinking file size on the disk, but now that I've re-read your original post, it seems like you might be talking about something else.
Also, when you say you have a camera that's not 3d, I really don't know what you're talking about.