There's no reason to harvest early or based on foxtailing. If it's spindly trash you can always trim it off. If it's solid, knobby buds, it's fine.
if it's all over, it's probably a genetic predisposition. If it's just at the top, then reduce light slightly or better control temp/rh and it might handle the light better...
every seed is differnt. unless this is a clone you have to read and react and not assume it's the same length as any plant before. Lots of plumping left in the 2nd picture, so i would say it's got a fair amount of time remaining.