EXS 24 Logic Sampler Users Group

I'm selling off a couple of my synths to make room in my studio. 
They're old, but they each have a bunch of sounds that I have used in
the past and would like to continue using, so I've decided to sample
them.  One of them's a percussion synth, so it wasn't difficult to get
those recorded, but I'm uncertain about the other synths.

Is there a general rule for what notes and ranges to record?  Looking
at the samples in my Logic/GarageBand collection, I see different note
ranges.  Some of them are sampled in whole steps (C, D, E, F#, G#,
A#), some in half-octaves (C, F#), some in quarter-octaves (C, D#, F#,
A).  I'm inclined to go for thirds, as that seems like a commonly-used
range and would result in sample sets that aren't too huge.  (I'm not
concerned about velocity ranges for these sounds, as most of them
don't have any significant differences, other than volume, when hit
harder or softer).

Are there other factors I ought to consider before using this approach?

Thanks!

-N