I'm just testing how long after the use by date they stay accurate. I'm up to a month, so far. Absolutely fine. The reader has no idea what the use by date is. I'm challenging the concept that a sealed system based on microelectronics suddenly goes bad on a certain date. When I've found the safe limit, I'll let you all know. (I'm checking against fingerpricks, admittedly on the reader, but not being a conspiracy theorist, I'm taking those as accurate).
My guess is the real limit is around three months after the end date, and they are taking an ultra cautious stance.
Do not try this at home, I used to be a doctor, so I'm mad enough to try it in the interest of humanity and the public purse. (And can afford it)