May I suggest a passthrough (plugs into USB)? If your computer can't handle it, there are USB power things that plug into the standard wall outlets. As long as you have electricity, you can vape.
I started with 360mAh 510s--6 batteries (clearance sale) and 2 chargers.
2 18650 IMRs came with my Lavatube 'kit'. (1 month in)
Then got a pair of 'eGo 18650 upgrades' and 2 eGo passthroughs. (2 months in)
Used the battery not in the Lavatube in one of these. Found myself with 2 batteries needing charge, and no spare. Picked up another 2 IMR batteries. and eGo charger. Built passthrough using variable voltage power supply from electronics bench. (3 months in)
Then had 1 in Lavatube, 1 in each eGo, all needing charge, and remaining one in charger. Put eGo charger to work.
At 1 year in, saw vendor with 18650 IMR sale. 4 more (8 18650 IMRs) Started looking for charger that could handle more than 1 battery at a time. Also picked up a pair of Bolts on sale (as backups).
Found charge/battery combo on sale--protected 18650s for use in Bolts.
Today's totals:
Mod batteries: 8 18650 IMRs, 4 protected 18650s, can charge 5 batteries at a time (1 in one charger, 4 in the other)
4 of the 510's still work
2 eGo passthroughs
Lavatube, 2 eGo 18650 upgrades, 2 Bolts.
Homebrew passthrough.
I agree with Hoosier on the magic '5' number. With a single charger, I returned home from a 2-week vacation (where I was unable to use passthroughs) with 3 batteries needing charge, and one mostly drained. Need to get the 12-volt cable for my new charger next.
...Bob