[Elecraft] Two battery questions - K2 portable operations

[Doug Forman]

I'm assembling a portable kit in which I can fit two small sealed 
lead-acid batteries.

For my specific size requirements, I have the option of putting (2) 12v 
(3.0Ah) batteries in parallel, or (2) 6v (3.0Ah) batteries in series to 
obtain the 12vdc I need.  (the specific batteries I am considering are 
the PowerSonic PS-1230 - Mouser # 547-PS-1230 or the PowerSonic PS-630 - 
Mouser # 547-PS-630)

It seems to me that with [ 2 x 6v (3.0Ah) = 12v (3.0Ah) ] while [ 2 x 
12v (3.0Ah) = 12v (6.0Ah) ].  Maybe the simplicity of this makes me 
question this assumption, or maybe it's been too long since I did these 
kinds of calcs  ;-)

Could someone please confirm or deny my thoughts here?

Also, I'm trying to calculate (roughly) the useful battery capacity 
based on considering the minimum current draw from a rig, and the 
maximum current draw from the same rig.  For example, given the battery 
configurations above, and considering the K2 approximate minimum current 
draw of 150mA and approximate maximum current draw of 2A (at 10w), what 
is the potential operating time ranges available from the batteries?

Thanks in advance & 73,

Doug  N7BNT