The location of a humidor matters more than its quality. A premium cabinet on top of a refrigerator will fail; a tupperdor in a cool corner will succeed. Placement determines whether the conditions inside the box are stable, and stability is what cigars want above all.
Four places to avoid. First, on top of a refrigerator: the warm exhaust at the back cycles the humidor’s interior temperature. Second, near a radiator or heating vent: the dry heat will pull moisture out of the wood every time the heat kicks on. Third, against an exterior wall in a cold climate: the wall conducts cold from outside, which causes condensation on the inside of the humidor in winter. Fourth, in direct sunlight: the wood expands and contracts with the daily temperature swing, and the wrapper colour can fade.
What you want is the opposite of all four. A consistently cool corner of an interior room (an office, a study, a finished basement) is ideal. Sub-seventy degrees Fahrenheit, with no draft from a window or vent, and no direct sun. A closet is fine if it is on an interior wall and not near hot water pipes.
In cold dry climates (Calgary, Minneapolis, Helsinki), winter is the hard season. Forced-air heating drops indoor humidity into the twenties; the humidor compensates faster than the room around it can. Run the larger Boveda packs and check the gauge weekly through January and February.
For more on humidity, temperature, and stability, see How to Rest a Cigar.