It depends on the strain. Some flower much faster than others. For example I just spent 20 weeks flowering a sativa while there are strains that flower in 8 weeks.
There is no answer to your question without more information regarding the genetics, how big you want the plant to be, indoor/outdoor, etc..
Oh right . The reason I'm asking is it's my first grow and they are quite small plants. I started from seed and it sounds like I'm just being inpatient lol, it just seems like it's taken forever .
Thanks for the reply though it all adds to the understanding of growing this wonderful stuff