How many images would you expect smush pro to process per minute?

I am running smush pro on a existing site. I am wondering about performance. It is a wp engine server. Shared.
I have been timing the smush progress. It seems to be about 45 seconds per image. By my reckoning for the 40,415 images it says it will process I am looking at 3 weeks of continuous processing!!
Does 45 seconds per image seem slow? Any ideas on improving that? What sort of speeds would you expect from Smush pro?