Some pure landrace sativas don't stop stretching but that's been reduced a lot in commercial sativas thanks to the bit of indica in mostly sativa hybrids. Indicas stretch around 100%-125% and stop stretching at 2-3 weeks, mostly sat hybrids are around 200% stretch and last around 3-4 weeks. It all depends on the strain and phenotype being grown. My s.a.d is 2 and a half weeks in and has stopped stretching it's pure indica. Nobody would really wanna grow a pure sativa that stretches and stretches and takes 14 weeks to flower unless you get well prepared for a headache. Watch out for those hazes too they like to try kiss the sky.