Never had a problem with the mags other than straight after overhaul! After the overhaul we broke down twice as the impulse spring stuck and we couldn't start the engine on the ground. It was very annoying and the second time we were away from home and by the time we got going we were racing sunset to get home.
A little trick from our maintenance organisation - wind the prop back twice then forwards, which appears to have released the spring and got us going. NOTE: They say DO NOT try this on a Continental engine as it will shear the vac pump shaft apparently.
Yes there are some good articles by John Deakin (search Avweb) about leaning on the ground, in fact he advocates doing the run up with highly leaned engine as this will tell you far more about the state of the mags and plugs than at full rich.