There's a crayon like thing called a Kool -Stik. Goes on the cutting wheel as it's spinning. As you have stated, these high speed cutters necessitate taking very small bites into the blade or else you will burr the tooth.
They all spin too fast in my opinion although I have never used the $500 Oregon they presently sell. A slower but torquier motor must cost more than the high speed inertia type motors most seem to use.
The largest benefit to me was that they straightened out the angles which tend to get a bit out of angle with continuous hand filing. I never sharpened chain when I was working so I'd come home and at night, sharpen a set of chains for the next day. Mostly a logger simply felled wood with the only "bucking" being done if you wanna call it that, was to remove the crown. Good chain lasted quite a while and the best chain i used then was Stihl.
As far as your initial question: A chainsaw, after awhile, can back out it's setting adjustment screws and make the saw run rather rich. I never owned a chainsaw more than a couple years to start messing around with higher out-put but I always had something to adjust the carb with to pick up those few rpm's lost over time. Eventually the saw would simply lose too much compression where no amount of adjusting did much. It was time for a new one.
