My clay was very useful, and I put it to work a lot; however, after a month, you could tell it was drying out. It's as hard as a rock now. I reccomend getting a smaller container to use in a small period of time!
I have used these exact brushes exclusively for over 30 years teaching art to students from kindergarten to college. They hold up extremely well, if washed properly. They also hold a point and can handle a lot of paint at once. If taken care of they can last for years of continuous use. Students appreciate their quality and get much better results with a higher grade of brush, I cannot believe that Loew-Cornell has discontinued making them; so get them while you can find them.