Hiring manager here.

Knowledge has a half life. If you have taken 6 months off, and have an interesting story, this is not a big deal. (For example, I took 8 months off to live in Istanbul. I had two interviews and two offers when coming back, one of which was completely outside my network.)

However, I had also just taken a month to do a functional course, and had worked half-heartedly on a startup that went nowhere. I had a story.

The longer you take off, the more of a story you will need, even if that's "in the last 3 months, I built a small toy to get myself reacquainted with React and Python" even if this is a Rails omakase shop.

Or, that story may be something completely different. All I care about is "can you hit the ground running?"

So what is the half life constant? Does it also apply to skill or only to knowledge? Are you hiring knowledge or skill?

My breaks have mattered “occasionally” with a few companies but by and large what you say is correct and it barely made people scratch their chin more than a few seconds, and I've had breaks (intentionally) of anywhere between 2-4 months every couple of years.