I think you can disable SketchUcam for normal work on large files, this should speed it up. Then you can create a simplified copy of the file and turn on SketchUcam so you can create Gcode from it.

To disable it (without uninstall)
Window
Preferences
Extensions
and untick SketchUcam in the list
restart Sketchup

 

Hi
I have been doing some experiments and it looks like the time is being taken up by the 'upgrader'.
The upgrader looks at all line segments in the drawing and changes their properties IF they are currently in a SketchUcam version prior to 0.919.
since you are obviously using the latest SketchUcam, and you are unlikely to open very old files that are coded in SketchUcam V0.918 you can disable the upgrader with a little editing.

Open the file
(Sketchup 8)
C:\Program Files (x86)\Google\Google SketchUp 8\Plugins\Phlatboyz\Observers.rb
(Sketchup 2013 to 2016)
C:\Users\yourusername\AppData\Roaming\Sketchup\SketchUp 2016\SketchUp\Plugins\Phlatboyz\Observers.rb

and comment out the updater by changing this bit (use Notepad or similar plain text editor)

Code:

  def onOpenModel(model)
  PSUpgrader.upgrade
  PhlatScript.setModelOptions(model)
  model.add_observer(PhlatScript.modelChangeObserver)
  end

to look like this

Code:

  def onOpenModel(model)
#  PSUpgrader.upgrade
  PhlatScript.setModelOptions(model)
  model.add_observer(PhlatScript.modelChangeObserver)
  end

save the file, and if Sketchup was open. close it, then open Sketchup.
Now loading large complicated files should be very fast.

BEWARE! I have not done extensive testing of this change, but it seems to work ok.
IF you do this you WILL have trouble if you load a very old file such as one might download from this forum.