My 10 year old watch with saphhire glass still has no scratches on the glass.
I was not carefull at all...
Mine too(but it's only 5 years old)
My wristwatch has a sapphire crystal lens and there's not a single scratch on it.
It's about 15 years old now.
Yep, your watches aren't going to scratch unless you enjoy rubbing sharp Diamonds on them.