At the end of the day people will cherry-pick the box(es) that they come across for the figures that they want multiples of. It doesn't always mean that the ones you want will be picked clean - I loved the Crash Test Dummy from S1, and have a fair few of him.
On the score of Spartans and Elves, I'll admit that I've got quite a few Spartans (33) and Elves (21), but I have never taken more than 1 of these per box that I've found. As you can tell, I live in a well-stocked region for minifigures (8 WHSmiths, 6 Argos stores, 3 TRU stores, 3 Tescoes, and about 9 independent toy sellers all packing minifigs.).
Bottom-line: everything in moderation