I don’t think there is such a limit, but more a case of the available RAM on the system.
Autodesk said it improved workability for model up to 1Gb with the recent version, but in general it is better to keep the Revit files below that (800 Mb)
That’s without external files, of course.
If you do not have access to Revit, one can create a project in Trimble Connect for Desktop and add the Revit file.
Then create a view and select only what you need in SketchUp and export that as a TrimBIM file.
Though the organization is slightly different, one can come up with a workable file in SketchUp.
Check this thread about another Autodesk format:
Is it possible to share any of the models that you have tried to import that have failed? I have not had issues with large files failing to import but I have never imported a model larger than about 700Mb. I would like to see if I can get them to import or if it fails for me as well. I am unaware of a model size limit but I think @MikeWayzovski is likely right about it being more of a case of available RAM.
The large models you are getting, were they created by merging multiple linked Revit files? Often architects will have a “main building” model with the units or interiors as linked in models as well as structural, mechanical and other models linked in. If this is the case it might be worth asking if you can get the models and linked models separately instead of all merged into one. The Revit Importer includes Revit link support and I have had success with importing multiple linked Revit models, that if merged would be a 2-3Gb Revit Model, into a single SketchUp model.