Smoking a pig at 225 F vs barbecuing one at 250F?
You may want to check out the following pages:

What Influences Cooking Time

Thermodynamics of Cooking

Using their methods, I have not had a shoulder take 15 hours to come to temperature at a smoker temperature of 225 (computer-controlled). I have never done whole hog, but as Jefromi stated the actual method of cooking makes a significant difference. The Hawaiian imu (the bury-it-in-the-ground style of cooking using the retained heat from sand and rocks that were under the coals) is a much more efficient way to rapidly transfer the heat to the meat than using air to conduct the heat, and forced convection from the blower in my smoker is more efficient than natural convective currents. If my smoker did not have the blower it would take longer to get the meat to temperature, but I still don't think it would take 15 hours for a shoulder.

Whole hog weight versus time at 250 degrees:


40 pounds: 3.5 hours
75 pounds: 9 hours
100 pounds: 12 hours
125 pounds: 15 hours
150 pounds: 18 hours
175 pounds: 21 hours
200 pounds: 24 hours


From Goin' Whole Hog

AmazingRibs.com is essentially a peer-reviewed barbecue site. They don't publish a recipe until it has been tested multiple times and is nearly foolproof. They also bust some of the barbecue myths that have been spread for generations. I am not affiliated with it other than donating some money to them due to their high-quality articles.