Every small engine I own runs full throttle when I'm using it.
I thought small air cooled engines actually cool better at 3,000-3,600 rpm.
I had an twenty year old 18 hp chipper, and our son has a three year old 10 hp snow blower, that do not have throttles. Wide open or off.
Our quad is a 2005 Polaris 330 Magnum with a Subaru Robins that runs 4,500 to 5,000+ rpm regularly. It is oil cooled/air cooled.
The 20 hp twin cylinder Honda jrider has is 'forced lubrication' with a filter, vs splashed lubrication on most smaller engines. I ran my TW-6 full throttle after a short warm up each time.
Most heavy equipment that is hydraulic, have manual throttles to keep the revs up and pumps functioning at necessary flows, excavators, cranes, etc. including my piggyback forklift. It has a 60 hp Kubota that just runs hydraulic pumps.
As for 'dregs' many drain plugs are magnetic, and frequent oil changes should cover the rest if you change oil after use when the oil is freshly circulated and warm. There is still oil in the pump, and in our Polaris quad, there is probably quite a bit in the oil cooler as well.