I ran into the same issue with a few large work groups using 9300's. They were used to scanning stacks of 25-50 at a time. Then they asked OCR to be enabled as default and were upset at the processing time.
Here are the options i went with...
workgroup #1 got seperate scan templates with OCR turned off (about 50% of their scans required OCR)
workgroup #2 was educated on how to enable OCR when needed. i even typed out a small work instruction with pictures, laminated it and put it in a plastic pouch attached to the printer.
Giving different options is your best option in my opinion. If i got a dollar for everytime i heard the "just put more ram in it" comment i would be a very wealthy man :)