I have this issue when exporting several images from a large SketchUp file. I’m usually exporting large 24x36" images for display on boards. I’ve tried to use the animation feature with 0 second transitions, but have found that takes a really long time and ties up my computer.
Basically, the first two exports work fine and export out in under 15 mins. As soon as I export the third image it ends up taking hours… sometimes 5+. It’s gotten so bad that I often open SU 2014 and export two images at a time and work on other things. It’s always the same. First 2 images less than 15 mins. The next exports are 3-6 hours. It doesn’t make a difference if its pngs or jpgs.
I’m running a 3.2 Ghz iMac with 32 GB RAM on El Capitain. This was also an issue with Mavericks.