Why not?
I’ll assume that your not asking Aries why she never heard of twice in seven years, so I’ll answer.
You’re assuming that you get to pick which seven years to look at, but it has to be true about any seven year stretch. Say for example, that you had them checked in year 0 (when you bought them), year 6, and year 12. You would say that from 0-6 they were checked twice, and from 6-12 checked twice. However, from 3-9, for example, they were only checked once.