If you are a 'purist' you will only use cotton. Crazy quilters and art quilters use anything that works. If you bought good quality material, it should outlive your lifetime, so I would not worry about it and get stuck into the love of quilting - enjoy and don't be restricted by stuffy rules. The only time I would worry is if you wanted to exhibit in particular shows - then you would need to abide by the guidelines. Hope you have many enjoyable hours.