As long as the mothers are mature and healthy it shouldn't matter at all. Most genetics take somewhere between 4-8 weeks to reach maturity from the established seedling stage. After that point you will be good to go. I used to run a SOG where the clones I used came form established mothers, and only would veg for about 2 weeks basically to build a strong root system. Then they went into flower at about 7-8 inches tall. They would end up 25-30 inches tall and average around 20g dried per plant depending on genetics, some would produce over 30g.