Interesting take on the 7 years myth. I've heard of it, but never thought about it much at all and certainly not in cellular terms. I always took it as an approximation to when something (minor) changes psychologically like our taste for food or music for example. Let's see...

When did I stop liking chocolate? - Never actually. Just no praline collection box, please! OK, still waiting for this one then. Bad example.
When did I start liking Sauerkraut? - Ah, 21 might be a good bet. We're onto something.
When did I get into metal? - Hm... mid-20s. Oh, we can make that work. We just calculate the mean of 14 + 7 (10.5) and add that to 14, i.e. a multiple of 7. That makes 24.5. Sounds about right.

Yeah, the myth must be true. 😮

On another note, do we not experience quite a few changes in life every 7 years, especially in our younger years?
In Germany school starts at age 6/7. Next big thing is Jugendweihe or its Christian equivalent at 14 when you're told that you'll be an adult (surprise!) and have to act responsibly. 21 isn't a big deal in my world, but US Americans seem to make a fuss about if I believe Hollywood. Not sure about later milestones ... 28 marriage ... 35 kid ... 42 kid off to school ... 49 ... kid's Jugendweihe ...? Oh, a neverending cycle!

Yet another piece of evidence for the 7 year myth. 😎 😇