Define SEX ...then Top
There are times when one HAS TO top because of stretch...
No, never, unless you want to slow a particular plant down, just train her over. When you chop the top off a plant you loose the Auxin from the apical meristem, the top tip, so the plant must remanufacture these, setting her back 1 to 2 weeks, all depending on variety as the English cut says.