The rocker switch below the hazard lights is a warm up only, as it bypasses oil to make it heat up quicker, we don't use it in the tropics, but in colder environments it is a handy thing. I personally wouldn't use it as the exhaust brake, even though the exhaust brake is one of the functions of the warm up. You'd be best advised to use the exhaust brake on the stalk. I've run one with and one without exhaust brake use, the one that used the exhaust brake had dirtier oil than the one without, but we change the oil every 5000K, Filter @10000K. So for us, it made no difference with or without. Brake linings and wheel bearings and wheel cylinders are changed @ 40000K intervals, and there was no discernable difference for the one without the exhaust brake, but the trial was only 5000K. I'd imagine that if one was to go without using the exhaust brake, The gains made are minimal.
As most here are owner/drivers, we are all more cautious than an employee who is trying to maintain a schedule. I advise use the exhaust brake function only, and use the warm up function for it's intended use.