IMO if a lot of light is an issue in your space then you need to control it no matter what the fabric says. look at solar shades to control the light and the heat in a space .So 40 hrs means 4o hrs is as long as the fabric can sit in bright sunlight before it starts fading IMO pretty poor in most cases and without some sort of light control not only does fabric fade but flooring and walls too

You’d have to see this, as it won’t copy well... Kravet Smart 35361.101.0 | , Herringbone/Tweed White - Kravet Smart Fabric

Barb, I think you are being given the wrong information. Being an interior designer for over four decades (Yikes!) in NY, the term used in upholstery is off roll or railroad. Off roll indicates the way all fabric is weaved from selvage to selvage and is upholstered top to bottom so the nap urns down. Railroad is not a type of fabric, the term is used when (you are correct) you don't want seams on the back or front face and the fabric is turned left to right. I would be curious as to what fabric people are saying as to no warranty on the fabric. The only concern I would have is if a fabric has a high pile, like a velvet or mohair. But a flat performance fabric won't have any problems with wear and the warranty is for spills and stains. Did you actually read the warranty everyone is talking about? In all my years of design, there was only one issue with railroading a fabric and that was because of a print match. Pick a performance fabric and make sure your upholsterer runs it the same way on all parts and cushions and you will be fine with no problems whatsoever, for many many years. Your dilemma is news to me.

I have reposted it. Please check the fabric if you wish. Thank you!