its strain dependent, ive heard of some strains flowering in 2 days some that take a week + i have a skywalker og and a blueberry headband that showed sex around day 4 and 5
Plants mature at different rates, just like kids, but if you vegged for 7 weeks, I would think you're mature if not close, so you should see sex within another 10 days or so, my guess.
Actually whether I veg for 3 or 6 weeks it always seems to take around 14 days, some a couple of days more some a couple of days less. Sativas are usually harder to switch into flower mode than Indicas but as mentioned above it differs per strain as well.