Battery drainage on my flash

I have a couple 430ex II I use with my 60D. I usually use Energizer Ultimate lithium for them. They work fine and give me a good number of flashes before draining out. If I take them out and put it in a plastic case and use it next day, they still retain the juice...

problem is, if I leave them in the flash (even if the flash is turned off) overnite or for few hours, a set of brand new batteries will be drained out by next morning.

Is that normal?