Thank you for your post.
There are size limits and they can be reduced by the hardware that you are using. Here are some restrictions:
– maximum artboard size: 227 x 227 inches
– I’ve imported a 2 GB file before, however, it is slow and takes time to make edits, which is limited by my hardware
– There isn’t really a limit on layers, it will just depend on your machine and how much information your layers contains
The optimal size really depends on your hardware and what it can handle, if you would like, you can send the document you are using to firstname.lastname@example.org and I can take a look to see if there is anything I notice that can be fixed. Sometimes, the way that the data is ordered and stored on a file can really complicate things and make it difficult for programs to read.
Let me know if that helps or if you have any questions or issues.