I've grown NL#5 and a C99x NL hybrid that contained one other line as well... so ehhh I can't really offer any advice on veg time. I flower from either retired mothers or newly-rooted clones whcih means my plants are either vegged for TOO long until they show stress from living in the same pots too long, or not at all.
Veg until your plant is just les than half as tall as you would like it to finish, or until it is trained into the right form (if you are running LST or a SCROG).