Some thoughts on Vistalight (vistalite?) batteries

Have you ever seen the discharge graph for NiCd batteries?

It goes roughly:

|...............
V | :
| :
+====================
time

I can tell you that NiMH feels about the same.

The problem is that, as Murphy would have it, that
abrupt turn in the graph corresponds to the curve
you're riding down, in the rain, on the commute
home from work. You've just about got time to to
think "Hmmm, that light is looking a bit dull", and
then a minute later it's just about out. Maybe it
had been a bit duller earlier, but riding in those
dawn/dusk times it's impossible to tell.

This has led me to thoughts of other batteries. IMHO the
vistalight 'nitestick' is not too bad, and I think
for it's price it's good, I'm happy with mine anyway.
I must remember to charge it every couple of days though.

But each battery is only 2200mAh at 7.2V. Why is it
such a bulky battery supplies only 2200mAh? I must be
missing something. I know a photo shop that sells 2000mAh
'AA' batteries - admittedly AA is only 1.5 volts (which is
really 1.2V talking NiCd/NiMH).
Wouldn't 6 of these ganged together give me 12000mAh and
probably weigh the same as a nightstick?
Have I missed someting here?
Can someone suggest a better SLA alternative?

A nightstick battery (NiMH) costs about $70,
a pack of 4 2000mAh AAs (IIRC) about $50 with a charger.

cheers,
-kt