Why settle on 04/05 e60 with that high of miles. :dunno: I looked high and low and found an 05 with only 47K miles on it. Got a good price for it too. Keep in mind you will likely be replacing lots of rubber seals/gaskets if it was driven in high heat area of the country. I don't have the miles, but the years have taken toll on many of the seals. Good Luck with your search.
High heat part of the country? I might agree with rubber seals, although I lived in Chicago in the early 1980's when the air temperature (not wind chill) reached -27F. That was a lot harder on door seals, hoses and belts than 115F in Phoenix. UV is the killer in Phoenix for plastic, rubber and paint. I garage my cars and keep the Gummi-Pflege and 303 Aerospace Protectant flowing liberally!
RE Gaskets - Once the engine has reached operating temperature, it is designed to run at around 105C (roughly 220F). An engine gasket at that point doesn't know the difference between an ambient temperature of 60F or 115F. In a cooler ambient the cooling fan may run less often and the thermostat may take longer to open initially, but a properly operating cooling system will keep the engine at around 105C.
The two real killers of gaskets and seals are long engine oil drain intervals, and allowing the car (in any ambient temperature) to overheat.
Follow BMW's 15K plan for oil changes and you are headed for disaster! Gasoline and other contaminants accumulate in the oil and the oil becomes acidic, breaking down gaskets. Sludge can also build as the oil runs out of additives required to keep contaminants suspended.
Overheat the engine and the aluminum components over-expand, breaking gasket seals.
Change your oil every 5-6K miles and keep your coolant system in tip-top shape and you will have a happy engine and receive long service.