Right now all I have is my 510 and a 510 Nicostick. I sent my Chuck in for a makeover (changing the graphics and paint for the heck of it

).
I've also ordered a Little Chuck and am on the list for a SuperT2.
So pretty soon, when I am out and about, I'll carry my Little Chuck wherever I go. I'll carry my Chuck whenever I need something with a really long battery life. I'll carry a Nicostick as a backup, with another sitting at home for a backup. And I'll use the ST2 here and there, as well. My stock 510 batteries will either sit in a drawer just in case of emergencies, or I may rip them apart for the connectors to make other mods.
I usually carry around a USB case with extra batteries, a bottle of juice, and a few empty carts with blue foam filler. My carts last so long with the blue foam that I only replace the filler once a week, and I'll keep using the same cart the whole time.