Gotcha. Hmm... We'll go with the Golden Rule: "How many licks does it take to get to the center of a Tootsie Roll Tootsie Pop?"
The world may never know, but 3 seems to do the job.
Maybe 4-5 if he's really adventurous or digs the whole seasons/occasions argument. You could even suggest a few scents along these lines:
1) A good all-purpose scent that everyone is wearing, 2) a casual scent [read "sport" flanker] that everyone is wearing, 3) a formal/evening/special occasion scent that everyone is wearing.
3 inoffensive mass-market crowd-pleasers will give him just enough variety. (Did I just contradict myself?) If you know him pretty well, you could even suggest some real fragrances he might like. (You know what I mean.)
We have to face the reality that some people out there just aren't "into" fragrances. They merely want a generic smells-good accessory, an easy spritz. Horrifying, but true. A dull and colorless life? Undoubtedly. I'm sure we could come up with plenty of epitaphs for such a sad, sad individual... but I think "Non-BaseNoter" says it best.