Is it true that hair salon scissors have a self sharpening blade that does not need sharpening?

I am going to open a business of sharpening blades. My partner has done this like 15 years ago. I have been doing the market analysis to see if there is market to our service. I've been told that although clippers need to be sharpened, the hair salon scissors do not. My partner insists they can be sharpened. What do you know about this? Thanks!Is it true that hair salon scissors have a self sharpening blade that does not need sharpening?
I have a good friend who is a hairdresser in a salon and she says that she has her shears sharpened every 90 days.