We would recommend taking them off every week or so and just wiping away any water that collects behind the magnetic. As with anything metal, if water stays in contact for too long it's not good for it. If it's been raining a lot, occasionally salt in the evaporated water from the roads can leave a white powdery substance, but It wipes off easily and does not cause damage if removed.Humperbumper.com does not recommend applying either magnetic or vinyl stickers to repainted surfaces. Disclaimer:We have never had any issues or complaints about our product damaging a surface, EVER! However, we are obliged to state that Humperbumper.com is NOT responsible for any damage to a persons vehicle or property due to the use of an adhesive sticker or car magnet. Additionally, Humperbumper.com is not responsible for ANY event arising from the displaying of our stickers or magnets. It is the sole responsibility of the customer to use best judgment regarding the display and usage of our product.