If you blow it up on the second day - around two days!
My 92 explorer has around 170,000 miles and the motor is still very strong. The trans and interior bells -n- whistles are another story. If your willing to put a few bucks into it each month and an overhaul of the trans every 120,000 miles or so it will last indefinately. As long as you keep the oil changed, do a tune up every 30,000 miles or so and replace sensors that go bad a 4.0 motor will last a very long time!