It has been about a year, since I noticed IMCE upload is damn slow when uploading images for my photo stories or just any other articles. For a very long time I was convinced that it's some cdn or JavaScript incompatibility (because sometimes, just sometimes IMCE upload worked just fine)
It was until today, when it started to take more than one minute to properly load that modal window of IMCE upload.
IMCE upload window
I quickly realized, IMCE folder was using about 1GB of memory (default upload folder -/sites/default/files) which stored more than 7,000 images - each time IMCE had to do a check up on all those files. I decided to look on IMCE settings, can I change default upload folder and start fresh? Luckily I was able to that:
From IMCE config - admin/config/media/imce/profile/edit/1 - create a new upload directory for IMCE
IMCE upload directory
Woila - after applying new settings - IMCE was blasting fast again. Hope this helps.