Plants that spend six to eight weeks in veg usually show sex before the flip, while ones flipped at three weeks force you to sort them in early flower when it is more disruptive. Giving regulars that extra veg time costs electricity, but it means males leave before they take up flowering space. The trade off between veg length and total run time is worked through with actual day counts at
https://breederregularseeds.com, which settled an argument I had with a mate. My rule now is no flip before preflowers.
