my 2 cents- the oil bath is a liquid filter- in one side down thru the mesh metal filter down into the oil and back up to the carb. K & N filters are also oiled to trap most of the dirt. The crank sits in the oil pan, the bearings wear on the crank allowing your crank to drop into the seals and damage them. This is why no engine shop will warranty seal replacement alone. The crank needs to be machines and new bearings put on it. We use speedi sleeves along with the seal replacement.
As engineers have continued to earn their jobs- better things have come out on the market - however finding it is time consuming. Some places that make it easy to find an alternative are outrageous on the pricing.
If you change your oil religiously (as is recommended as with your vehicle) in any application you lengthen the life of the motor.