Hi, in regards to oil coolers, I've ridden my 1975 stock cb750 in stop and go traffic quite a bit here in Chicago. One day it was well over 104 degrees, and I had no problems. Most late July and August days float between 80 and 90 degrees here. I do run 20w50 castrol motorcycle oil, and I change it around 3 times a season (I ride between 10k and 15k a summer). The only mod I have done to my bike is a billet oil filter mount, so that I can use spin-on oil filters from a 2004 toyota tundra. I bought it off ebay for $45 and it makes my oil changes much easier (my original filter housing's bolt stripped and this was a cheaper alternative, and it looks pretty good).
Of course, an oil cooler is never a bad idea. I was considering installing one because they are relatively cheap and simple to bolt on. However, I wouldn't consider it necessary.