To Grey or not to Grey!?? That is the Question!!

Whilst chatting with a fellow blogger on the subject of the appearance of grey hairs, it occurred to me - when does a lady just succumb to the grey and no longer fight against it with hair dye?  When do I just become a 'silver-surfer'?  OK I'm turning 41 in 3 months time, but nevertheless have rather a lot of white, not just grey, hairs just springing up all over my head!  Foils and tints at the hairdressers just don't cut the mustard now, so last year I succumbed to an all over permanent to hide the white!  However judging at the speed with which the little blighters re-appear, it's going to take money and time to try and maintain a youthful look!  So ladies, when is the age and for what final reason is it that more senior females amongst us sport the 'looks-like-my-lovely-Nanna-look'??