As far as I'm aware, the qualification periods are always 2 year blocks based on the base date. Therefore if, for example your base date was 30 June 2015, then your current qualification period is 1.7.2017 - 30.6.2019 and therefore you have just over six months to get to *G (30k or 40k). There is no rolling 24 month qualification period like I think you are hoping for that I'm aware of.