Years ago (1988) in 'Motorcycle Mechanics Vocational College" my instructor told us 'you have to ride your bike at least 10 miles to replace the juice in the battery that you used to start the bike'. Later I had an experience with a '85 Honda Nighthawk and a '79 FXE that made me think he was right. FWIW

. . . and yes, magnets CAN loose magnetism if subjected to severe vibration or 'hammering'