Like Cook22, I am very laid back about how my stamps look. Staining doesn't bother me at all, if they stamp well. That goes for rubber or clear.
I find when the clear stamps are a little stained, it's easier for me to see what the image/sentiment is when I am looking for something on the clear sheets or boxes.
Bugga in OK
"Be kind whenever possible. It is always possible." Dalai Lama