I've been working on some pieces lately that are very detailed. Illustrator has even crashed a few times, well more than a few times. It's because my files have been too large. That's not something I really ever thought about in Illustrator, Photoshop yes, but not Illustrator. Well, yes everyone, file size is a big deal. If I had looked at my layers palette I would have realized that I was duplicating layers without even knowing it. So, if you are having issues, slow down, and take a look at your layers palette. The issue might be from there.
Also, take a look at your piece as an outline (command Y ...View tab). Take a look at my image below. I didn't know I had so many things layered!
Hence - check your layers and check out Outline mode.