Compare the quality of photos that you would take at 1/150 shutter speed and then switch to sports mode and click the same images with higher shutter speeds. You may notice that there is a degradation in the clarity or quality of images as you go higher up.
Take a long exposure shot at night and compare that with your normal photos, if you feel that the longer exposure looks richer than you average daylight photos then you could ascertain the level in the loss of image quality of the sensor over time by reviewing the detail captured in longer exposure vs short exposure. You would be able notice some quality changes when compared with some shots you took from the early days when you initially purchased the camera to compare them.
Since this is an area of concern that has been shared by one more person verbally than my own observations, and too early to actually compare results or identify the degree of problem of various camera models, I would advise caution and fair judgement.
