As much time as we spend making a piece, I think it's worth the effort for acid-free. It's become quite popular and shouldn't be too difficult to find for a decent price.
It depends on a lot of factors. Temperature and temperature changes, exposure to sunlight, humidity and just about anything in the air that come in contact with the piece.
The color changes can happen in as little as a year. I stitched some designs for mt nieces when they were very small and when we changed them out just two years later the fbric was yellowed beyond cleaning.
For some pieces I don't think it matters. Characters for kids or items you think might be out of style in a year or two. The acid free mounts are inexpensive enough that if you think it might be something you want to keep it's worth the cost.
También es importante lavarlo para limpiar el apresto o almidón que les ponen a las telas, y luego plancharlo sin añadir ningun producto al planchado. El almidón o apresto hace que el bordado se vuelva amarillo
The color changes can happen in as little as a year. I stitched some designs for mt nieces when they were very small and when we changed them out just two years later the fbric was yellowed beyond cleaning. For some pieces I don't think it matters.