Some of us have eyes that don't permit that. From the point I started needed glasses I have only once gone a year on the pair I use for the computer--nothing wrong with the glass, it's just my eyes drift enough that they start giving me headaches. I usually get 2-3 years out of my progressives before they're too far off and need replacement. With an adaptable lens my brain simply automatically compensates as my eyes change, I only need replacement when the infinity goes wrong or as my astigmatism changes too much.