I think this thread wins the Darwin Award. While there have been some funny posts at times, presently we find ourselves discussing battery life as applied to sex toys!
And
buurin, it certainly may be "your business" as to what or why you own 30 sex toys. However, it's my priveledge to comment when such an off the wall subject is brought up in a forum that deals with the sensible part of your experiments... that part being batteries.
Vibrators are nothing more than a switch, batteries and a motor with an off-centered weight on the shaft; the same principle used in pocket pagers and vibrating videogame controllers. Perhaps the motors are so cheap that their duty-cycle cannot handle a quality alkaline battery. Instead the cheapo ones crap out before the motor overheats or the off-centered weight flies off! Let's face it... there's prolly more thought put into the exterior looks, feel, and finish than there is with the electro-mechanical aspect of the thing.