Yeah, if they are getting sold, their weight at that time goes on the pedigree. If they're not going to be sold, I update the pedigree at 6 months (senior age for 4 class rabbits, intermediate for 6 class) and again at 8 months (Senior age for 6 class rabbits).
Since some rabbits don't fully mature (finish growing) until 14 months, I may update it again.