it all depends on the strain.. indica and indi dom strains can go as short as say 56 days or so, and some sativas can go for like 14 weeks or maybe even longer.. there are a lot of other factors that play into it as well, like type of lights, nutes, growing style, etc...
at 30 days, i would say you have atleast another 30 days if not a lot longer to go before they are done... like i said though, it all depends on what kind of strain you are growing...