There are no conclusive findings, too many variables involved. For me I tried one and after a little fiddling I got it to MY liking. Some guys want an absolute air pocket to ride in while others, like me, like a little air flow on them. You can adjust them where they do make a difference.
Yes what Harper said. If it cranks but does not fire I'd say battery going bye bye. If pressing the button does nothing for a time or two, loosen the screws holding the switch housing together, pry it apart a hair and spray the insides with something like ACF-50 or De-Oxit. Don't use WD40...
Nobody mentioned repair. You mentioned "periodic maintenance", which is what changing pads is. Which is what cleaning bobbins is.
One of the main functions of the bobbins is to keep heat from the rotor's braking surface away from the carrier, avoiding warping. So "micro scratches" are a...
I clean mine every year doing my spring prep. I have a rubber "cone" that goes into a cordless drill. A quick shot of brake cleaner, stick the cone in the bobbin, give it a quick spin and done. Takes 10 minutes, never had any brake issues.
Did you spray the bobbins with brake cleaner as you turned them? They can hold quite a bit of crud. Otherwise they're fine, can't always turn them by hand. But as long as you "broke them free" you're good to go.
You have 2 threads going asking for help with the same problem. You received help from a half dozen guys here and no response. How about you post the solution so that you may help others with the same problem?