How durable are the batteries on bikes? My genius roomate moved my bike without my permission (violation #1-#100) yesterday, turned on the bike to do it (violation #101) so he could see if it was in neutral cause he's not mechanically inclined or knowledgeable of bikes (violation #102-#200) enough to just clutch it and push (violation #201). It gets better, then he forgot to turn it off with my highbeams on leaving it for me to find dead when I woke up(violation #201-#1000). So I had to use my car to get to school while I recharged the battery, LAME! Anyway, how durable is that battery? Cause for concern besides living with a retard?