I clean about 40 to 50 deer per year. Once the deer is on the gambrel in the air (not yet gutted) I can have it in the cooler in about 10 to 15 minutes. But that is having the tenderloin, backstraps, neck, hams, and shoulders in the cooler still on the bone.
After that I cut my steaks and all. I can't see how you could debone a deer in 20 to 30 minutes and feel like you have done a proper job.

That's just me.