Should I use different nozzles for different materials? I know I should use different nozzles for filaments that use vastly different temperatures but what about filament types that use similar temperatures?

For example, PLA and PLA composites like ColorFabb Woodfill filament.  Should I use a separate nozzle for that?
There is absolutely no reason to use different nozzles, not even if filaments do require different temperatures.

The only exception is when printing abrasive filaments (such as glow-in-the-dark and carbon-fiber) in which case you should use an abrasion-resistant, stainless steel nozzle. This nozzle can also be used to to print "regular" filaments but a regular brass nozzle has slightly more favorable properties if you do not require abrasion resistance.