HELP WITH FLOWERING TIME

can anyone give around about how long big bud x white widow is in flowering for am using 600 watt hps soil they have good air and feed.i am asking as i am going to be moving in a few months 4 or 5 and i want to go for a good size grow they will below riders 2 what are small and good on time i have done low riders 3 times b4 thats my 1st grows i was shocked @ how big my bb x ww leafs they could be doing with a bigger pots but i am coming up to almost 3 weeks in flowering the only soil i can use is for cuttings and seed could this be possible as it will put the nitrogen from the new soil in it any advise on this and my next grow would be grateful i also no not 2 plants are the same and the everyone has there own way of doing things THANKS