I can't really get the fix I need in one week, and it never is actually a whole 7 days anyways. I would say that 10 days and 10 days would be the best I could do. Last year we did 2 weeks, plus 2 days and it was super. If you can, add to that 2 weeks an extra day because then you actually have the full 2 weeks, not 12 with two days travelling back and forth to airports.
I would think that if I could go 3x a year, I might be able to keep the vibe so that one week at a time would be enough.
I need days and days of nothing and then I get my second breath and like to explore - in one week that doesn't happen. Clearly, if you are staying at a resort and mostly go back and forth from the beach to the bar, one week might suffice!!

I have only gone on a one week vacation once and that was 20 years ago - to Antigua. It was pretty low key but my hair will still wet from the pool when I was walking across the tarmac to get on the plane and I was crying....not a pretty sight!