They STRONGLY advise. If you have 6 kittens then try work it with their new owners so 2 go at 13 weeks, 2 at 4/5 days later, and 2 a 14 weeks. That is staggered then.

I would NEVER buy a kitten unless they were 13/14 weeks of age. My new kitten will be coming to me at 16 weeks of age.