Is it possible to become resistent to dbol over time, and if so what kind of time frames are we talking?

The reason for this question is that I have used dbol several times since beginning my steroid oddessy and have always had good luck up to my last 3 cycles in which I felt absolutely no kick from it. I don't believe it was bunk the gear looked right anyhow, and I when I switched suppliers got the same stuff from another with no noticeable difference. The last thing I did was switch from BD to naps and still nothing, bear in mid these were at 50mg ed doses.