A humidor is a convenient and aesthetic display PRESENTATION BOX used to "merchandise" a representative assortment of your cigars. Because it's out in the open, and residing with our other furniture, we invest more money to buy something aesthetically pleasing.
But a box is just a box. Why spend more money on fancy storage when you don't have to, when cheap large volume storage in the form of a coolerdor will do?
Case in point, a $600 Reed and Barton Biltmore humidor which stores 100 cigars means that this storage method equates to $6 per cigar. Contrast that with a $60 coolerdor that will store 600 cigars or more, translating to $.10 cents per cigar.
We can only smoke one cigar at a time, more or less. So, my belief is that the way to go is to store your INVENTORY in "backstock" in a coolerdor (just like they do in a retail store), moving only a handful of representative smokes to the expensive humidor for ease of access.
Spending hundreds or thousands of dollars for multiple humidors because you've outgrown them is overkill, IMO. And, if you buy only ONE humidor, you can afford to concentrate more of your budget into one REALLY NICE one, rather than three or four mediocre ones.
