It works, what to say? Recalibrating is necessary since the display changes over time (aging, shifting of parameters etc). Between 2 months I couldn't see much difference, between 6 months the difference was visible. It also depends on quality of display.
I use a Spyder2 Express and calibrate every three or four months. Great results.
Note: Not all Spyders are equal. Caveat about the Express (from the manufacturer):
Spyder2express uses an earlier generation of Spyder technology. It is excellent for calibrating CRTs and typical LCD displays. For laptops with very narrow viewing angles, LCDs with gloss finishes, and new LCD technologies such as LED backlight and Wide Gamut displays, we recommend Spyder3-based products, such as Spyder3Pro.
If you are using laptops with LED displays (I think they call it WLED), then you will need the Spyder3. I sold off my Spyder2 and bought a Spyder3 because I bought a laptop has a WLED display. With the Spyder2, there was a slight colour shift after calibration. The Spyder3 works great with WLED.