One of these is a good investment:

its an american thingie called a "balsa stripper". (company is "Master Airscrew")
you use it to cut same-width stips of wood off sheets.
So take a sheet of balsa or basswood, turn the dial until you've got the thickness youw ant, then run it own the side of your sheet of wood - voila! one strip of wood.
Obviously this lets you replicate that strip size over and over again. Its also graduated so that you measure extremely accurately the width you want to cut - one turn of the screw is 1/32 of an inch.
Possibly in my top10 of all time great tools for modeling. it can also cut foamboard and light foams, thin styrofoam, expanded PVC and similar.
cant recommend it enough.