It is a sad but true fact that battery powered vibrators tend to be poorly thought out, and have a built in obsolescence. While there are always exceptions to the rule most battery powered sex toys will last between a couple weeks and a couple years. More reputable sex stores will offer some sort of warrantee with their products (the standard seems to be about 30 days).
In addition to some preventative measures there are a few common problems that can be easily checked that may bring your toy back to life. Most problems that can be fixed are related to the batteries and the connections inside the vibrator.