I use an oil cooler. It's unlikely that you would cook the motor without one, but using one will help maintain a constant engine temp, therefore the engine will run on tune constantly.

 

I installed an oil cooler on my 07 heritage when I had 10,000ks, I have now done 112,000ks and no problems

What I did was, I bought the HD oil pump fittings that are a straight forward simple fit behind the oil filter, takes maybe half an hour to fit. Then I went to Super Cheap Auto and bought a small universal oil cooler. It fits below the regulator on the frame. It is also probably one of the few items you can get from the wreckers that will fit a HD.

It's all an easy fit job so the potential benefits far away cost and inconvenience.

I just bought a Jagg oil cooler off rolly speed shop for just under $500 with oil filter - delivered within a day - the one I got mounts up on the down tube of the frame so its out of the way of stone damage etc... - around town it dropped my oil temp by 20F and on the highway by 30F

well made product very easy to fit - took no more than 1hr start to finish

apparently if you have the 96cubic inch motor it spray oil under the piston to keep it cool - and thats why they recomend an oil cooler especially up here in Nth Qld in the tropics

where the oil temp can be up to 30-40degrees before you start your engine.