The minute it begins to stiffen from age or the bristles start to change appearance such as getting crinkly or sticking out a bit. I find that the brushes start to harden pretty quickly so I probably replace Tibbe's every 2 - 3 months to be sure his gums aren't hurt.
__________________  Jeanie and Tibbe One must do the best one can. You may get some marks for a very imperfect answer: you will certainly get none for leaving the question alone. C. S. Lewis |