The ligth output of your right/left look a little bit different - left side looks a little dimmer than right. But I can only think it may be, you should know much better with your own eyes.
If you feel you have sufficient illumination, then it's great.
BTW, 20% loss of light output after a few years is not a guess, rather a scientific measurement, was told.
Originally Posted by DrX
One of these bulbs is 10 years old, the other is 2 years old.
I wouldn't say there's a 20% difference.