Help Wife Discretionary leave For 3 Years ?

Hi I need some help I am a British citizen and my Wife who I Married from Pakistan came to the UK in 2006 on a 2 years visa we also have 2 children know I applied for her indefinite stay to remain in UK but was to late about 3 months late and she was overstaying anyways because i was late the Home Office Granted her a Discretionary leave To Remain for 3 years which expires in November 2012. My question is when can I apply for her indefinite stay to remain in UK how many months before the expiry date ? I also have seen on some websites stating that if someone has a Discretionary leave they cannot apply for a indefinite stay to remain in UK instead a extension for another Discretionary leave for 3 years is this true ? because Discretionary leave has to be like 6 years or something before applying for a settlement in the UK. By the way she has done the "Life in the UK" course and has passed it but am not sure if this will matter or not