Break them out into separate files and then insert them into the main one as links. (mast document) this will make the main document more easy to manage. Just dont break the links!
You can also try Object > Path > Simplify in Illustrator. Removes a lot of the points that may not be necessary.
What application are you using to assemble the document?
If you use something like InDesign you can just place the vector files and it only includes the full file when outputting so shouldn’t be an issue. Same way books with 100s of pages of high rez images are done, they aren’t actually IN the file, but linked.
astute graphics also makes some illustrator plug ins that can help remove excess points.
You should first figure out if they’re just running slow because of your machine. If you have an older GPU you can adjust rendering modes to see if one performs better than the other by hitting Ctrl (Cmd)+E. GPU acceleration is typically fastest.
If it’s very complex and not just because someone was adding a lot of surplus points, and your machine is up to snuff, you can try moving objects you don’t need to layers and hiding them. Hiding objects should improve your rendering speed.
Lastly, you can check how much memory your system is actually using by either using Windows task manager or OSX Activity monitor. I’ve got some files I would consider very complex and even those only end up using a few gigs of ram at a time. FWIW I always found Illustrator performance better on OSX, used to always have tons of stability issues on my PC.