I had a lot of pain and numbness when I rode with 'moderate' CTS. I have none after the CTS release, as long as I keep my wrists in a relatively neutral position. I recommend seeking the counsel of a good hand specialist. If I had a problem after the surgery, I'm not sure I'd go back to the same surgeon, though.
You should be able to ride all day with no hand pain, CTS or not.
Have you ridden with CTS? My bike fits, and I had significant hand pain after 5-10 miles (depending on my mood) before the surgery. That was with 'moderate' CTS.