When I was primarily rocking the 510, I kept about a half dozen batteries in the 10-port multi-charger along with an always-always charging battery in the car (using the standard 510 wall charger hooked to the 12V USB via a mini-plug-to-lighter socket cord), and worked a three-battery rotation throughout the workday. I've never had a PCC--afraid I'd get lazy about keeping it charged.
Since I've mostly moved on to eGo, I'm the owner of just three eGo batteries. (The old 510s are my backup.) One used only during my long early a.m. vape, then back in the multi-charger w/ 510 adapter all day. That's a slow-ish charge for eGo batteries, but not too bad. Of the other two, one's a PT I mainly use when driving, plugged in or not. I also keep an eGo USB charger for the lighter USB socket and try to remember always to have it charging the non-PT battery while I'm driving and vaping the PT battery. So far, so good.