"Clone" means exact copy. It's not like a xerox copy machine that gets worse if you copy a copy. DNA is like a file on your computer. It's all ones and zeros, and that can never change, no matter how many times you copy it.

I have cloned clones of clones of clones of.... with no change in the plant. I have also read many times that people have continued to take clones of clones for many years and nothing undesirable happened.