Opening up a can of worms....
If you only ever looks at your pictures on the screen, then why does it need calibrating?
If you are using the screen to adjust white balance and brightness so that you can print, then surely you must have a consistent and predictable light level in your room as your eye will perceive different colours/brightnesses according to the ambient light that you are working in - so if you have a wind, you will need to calibrate every few minutes.
This is because the eye perceives reflective media (such as prints) differently to illuminated media such as screens and slides.