These before and after photos are from a furniture cleaning in Tampa FL. This seat is a part of a breakfast hutch that was heavily soiled by the owners children constantly putting their feet up on the seat while doing their homework. You can see the heavy dirt build up and oily stains from their shoes. The home owner said that this was one of the most used pieces of furniture in the home.
These pictures show how even heavily soiled furniture can be cleaned to like new condition. Not to say there hasn't been some fading of the fabric over time but it's minimal over the life span of the seat. As far as furniture cleaning goes this is an extremely aggressive clean. Most furniture doesn't get this much use and can be cleaned before major soil build occurs.