Well, you can go too far, a guy I know used to take his calipers off every couple of weeks, take the pads out, clean them to a spotless condition with brake cleaner, then run them on a piece of emery cloth until they looked flat, then he would take a toothbrush to the calipers, loads more brake cleaner, then he would clean every hole in the discs, clean the disc face with even more brake cleaner.
The result was his brake lever never felt good, was always spongy, his brakes squealed like a stuck pig and I always let him ride in front of me because his brakes were frankly rubbish.
He wouldn't listen, pads need to bed into the disc, they need to get "friendly" before you get a decent feel to them. But depending on the mileage, I'd say twice a year isn't too oiut of the ordinary. I use my bike every day to do a 180 mile commute to work and back so mine are cleaned every two weeks anyway, but I don't remove everything and remove all the working surfaces.
And I only ever use Red Rubber brake grease on my brakes. None of this copper crap because that stuff really shouldn't be anywhere near brakes, ever.