When does stretching stop (in flowering stage)?

Do they stretch for the entire flowering period (obviosuly more in the begining) or does it come to a complete halt after a month or so?
I guess i've never really payed attention to when they stop stretching..

2 to 3 weeks

That quick? And do they grow anything at all (height wise) after that or it's just bud formation after 2-3 weeks?

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.

Alright, thanks