Is this an exercise in estimating things, or do you actually need to build something?
First thing you need to completely specify is the battery - is it a rechargable Li, or some primary one - what's the peak voltage and what does it decay to at it's end of life?
Other than that, keep in mind that buck and boost converters tend to be 80%-95% efficient and LDO's efficiency can vary from very close to 100% (in dropout), all the way down into pathetically inefficient. Also, switching regulators do tend to burn more power (they'll eat up ~10mA or so of current just running, so be sure to factor that in).