A 17-element lens has 34-air-glass interfaces. That is 34 surfaces for light to bounce around and reduce image quality. Since "anytime you add something in the optical path you will lose quality", removing elements from a lens should improve image quality. Each element I remove from the lens should improve quality by removing two air-glass interfaces. Remove one element, and it becomes a 16-element lens with only 32-air-glass interfaces and the improved image quality to show for it. Remove another, and it's a 15-element lens with even better image quality.
Imagine the image quality when it is down to a 1-element lens. Then finally, the holy grail of image quality, which one cannot even imagine, a 0-element lens! It is so amazing, your mind simply cannot comprehend it. You will be in denial that this is the pinnacle of image quality. Here is a photo taken with a 0-element "lens":
The best way to determine the effect filters will have on your lenses is to take your own test shots.
After reading Good Times with Bad Filters, I decided to try the stacked filter experiment myself. I took test shots without UV filter and with five stacked multi-coated UV filters plus an uncoated filter for good measure. The filters looked clean enough, so I did not clean them.
Camera sharpness and noise reduction were set to default (0). Camera was set to Full Auto, so images were underexposed with poor white balance. I compensated with some mild post-processing to increase exposure and correct white balance. I did not increase contrast or apply additional sharpening.
Again, take your own test shots with your own lenses and filters to see the effects and to satisfy yourself that your shots will meet your own personal quality standards.