Depends of size of your LP tank. Using a 20lb tank, mine easily goes 20 hours on medium heat. Never had a single smoke go longer than 20 hours.
Not sure I understand the real point of the question. Naturally if you put it on the table it will be taller. Whether or not you should is another question. Is the table stable enough to hold this and a 20lb propane tank? Is it possible the table could catch fire? If the table is too tall you may not be able to reach the top rack(s) easily.
I think it is just plain steel. I've had mine for over 2 years and I haven't had any rust or corrosion issues.
I don't know what is the largest turkey that you could smoke, but I can tell you that I have smoked a 24 pound bird and it was the best turkey ever! We soaked the turkey in a brine for 2 days; then stuffed the bird with oranges, apples, pineapple, onions, and garlic. There was still plenty of room, but I don't know what is the biggest bird that you could fit in the 24 inch smoker. Good luck!
I didn't trust the thermometer in the front door. The more accurate way to determine what cooking temperature was being developed and maintained was to go with a probe thermometer inserted into the food. There are several on the market, but my first choice, from past experience, was from ThermoWorks. The door thermometer doesn't seem to provide any accurate detail, and changing it out still doesn't tell you what the food is doing anyway.
Yes..it is all well built.
29 1/2 inches across the front and 21 inches front to back. That's from the outermost edge
you will have to modify the burner, but I don't think you can as designed