Eighteen!

This is a new record... my most recent sensor lasted 18 days.

That's more than a day better than the most recent record holder.

Interestingly, one of the side effects of using them on my arm is that they seem to work quite reliably all the way to the end - and then they sort of crap out immediately... there is much less of a deterioration effect. It's still noticeable once you know what to look for, but much less so.