Particular attention for the chenille fabrics: never use water for the stain treatment. Only use the special glove (or dry cleaning if possible).
Glossy, lighter or darker, irregular shapes that spontaneously occur after (long time) seating on the fabric. This colour change doesn’t influence the quality at all, but can be bothering in exceptional cases.
Let’s be clear that this is absolutely normal, most common for the chenille and velvet fabrics. As shading doesn’t lead to a decrease in quality, this is no reason to any complaint.