This isn't answering the question but I agree with DL - have you spent any time on reducing current consumption? getting better batteries is good but using them less is even better. clearly, there are things that you can't do anything about (like motors) but it's always a worthwhile exercise. makes you a better engineer.
From your OP, I'd gues you have done uC based projects so there are a lot of things that you can do to reduce consumption, like DL said. use sleep when you can, turn off things that suck power, slow the clock down. every little bit helps. Also, look at all your circuits from the perspective of reducing current consumption. For example, if you are using dividers for a reference voiltage, make them higher (a 1K/1K divider produces the same voltage as a 10K/10K but at 10X the current drain). Using lower power parts is always good. Some peripherals have shutdown or low power modes.
Finally, get familaiar with Pchannel mosfets - you can use them to turn off major sub-systems. For example, you can use one to shut power down to things like transmitters when not in use.