Been using Eneloops and Imedion for years now, charged in a Maha Powerex 801 8 bay charger as well. Still using my first set of Eneloops from 07. They stay in the flash, and stay ready to use all the time. 2 430 EX's that I don't use often are nonetheless always ready to go.
Alkalines are the ones that will leak and damage equipment, it's rare for a NiMh to do so.
My experience with the Everready Rechargeables is that they don't hold a charge long, neither in storage or in use. I've seen a "Professional" that charged plenty using the Eveready's and having to recharge during a wedding. The guy actually had to run across the street and buy some alkalines during the wedding! I've shot many weddings and used the flash hard, after about 350 shots they come out of the flash hot, still working but need fresh ones for multiple flash scenario's like bouquet toss. I typically use 3 sets of 4 and take 1100-1500 pictures at a wedding, every one a flash picture.
I've never charge mine in the Eveready charger, and wouldn't, but the PowerEx charger uses a 1 hr charge and they've been fine on that.
When ordering batteries from www.batteryjunction.com
they usually send a plastic case for 4 with the batteries, just carry a couple of extra sets....you probably won't need em as 2 sets will more than likely get you a couple of thousand pictures when not taking rapid repeat shots. The real key there is to help your flash in bad conditions with an ISO bump so the flash won't have to output 100%, that'll ensure they last longer as well as taking better care of your flash unit. So in very dark conditions where you want a fairly small aperture, be sure to bump ISO to at least 400 to assist.