The ballast can tahan water wan cause it its place at the engine bay area. This doesnt mean you purposely pour alot of water on it. Ballast sure will kena water wan see have much water it kena loh...Mine also kena some when wash car but no problem. If want 100% go for ballast which is water proof wan. :D
Depends on ur usageand brand. Normaly will last for 2-3 years gua....