i juz dump it in my bag....
most modern flash have quench circuits to drain all charge from the capacitors when you switch the flash off. For those that do not, you can always press the test button to fire off the last charge after switching off. Even if you do not drain off the last charge, if left for some time, the capacitor will naturally drain off its own charge.
Just came across this post while searching for the CP-E3.
I keep my speedlite in my pouch provided every time I'm done using it. Then store them in the dry cabi. I'd suggest if you're not using it for a long time, just remove the batters in it, as you won't want any battery leaks to damage the circuitry of the flash.
I think whether storing it in the dry cabi or not doesn't matter much, as the intenal circuitry, including capacitors and such, are all enclosed inside the flash casing itself. It's just because I have space inside my dry cabi that I just dump it in. Even if you do not put in the dry cabi, it will still work as per normal.
Anything that can take pictures...happy already lor...(..but...Hasselblad_H5D-50 as my Workhorse)
I keep my 580EX with all batteries out of the flash unit in the dry cabinet.
I keep mine in the bag with fresh batteries ready to go at moments notice.