The 1fz has a oil cooler on it so adding another one would be overkill. It also holds about 8qt of oil vs other motors that hold 6qt. The motor doesn't seam to die from oil related problem unless you never check it.
Just as the towing package adds an additional trans cooler to the one already provided, an additional air exchange engine oil cooler is cheap insurance, IMHO. Engine oil removes about 25-30% of total engine heat IIRC, so even Mobile 1 deserves all the help it can get in places like the Mojave - again just IMHO. Of course, my viewpoint has definately been twisted by overexposure to race cars, Navy jets and spacecraft, so I have kinda lost sight of the concept of overkill. BigMac