Make duplicate image an instance, not a copy!
InDesign has this in place, and so should Illustrator :)
When you import an image file into Illustrator and copy it, it will make a new copy, instead of a new instance. If you work on a file where an image file is included multiple times, the Illustrator file itself often becomes too large.
This would never have happened if the duplicates of the image file were instances instead of copies.
It is also impossible to relink duplicates of the same image when they are copies. You have to do it manually. It's both time-consuming and outdated.
Turning the image file into a symbol is not much of help either as it still creates a new link in the links panel!
Do as in InDesign. It will help reduce file sizes and improve performance!