Function of the coolant and lubrication systems are still under work trying to get the engine damage parameters right, and have been revised/updated as part of the MkIII mod. The MkIa will change slightly when the later mod is installed
I found too, she doesn't die when holding the limit, but at least it drops off quickly like it should.
And yes, the operation description is more an aim of the work in progress, virtually copy-pasted from historical documents. It's not quite as strict as I make out...just yet but it will get there. By final release I plan to have it so if you don't fly the plane like it says, the plane will respond accordingly. I'm only halfway there as yet, but it's good practise. At the very least the guidelines show how to keep a cool engine ready for combat and how to get the maximum internal fuel range of some 1100km.
As is also a fact of real world engineering, short range missions can usually be flown under far worse operating conditions than the typical extended overwater flight of a Pacific mission. You might survive if you have to ditch over land, for example, and you can push the limits a little more, enter combat before the engine-oil has gotten hot in the first place and so on.
With the revision contained in the MkIII mod installation, try a full length mission overwater or unfriendly terrain exceeding an hour and see how pressing its limitations work for you then
