How often do you check your sensor accuracy?

This morning was a bit of a mess with my sensor. I changed it Saturday, and calibrated it once. I checked again before dinner and it was close enough.

Cut to today: my usual normal breakfast went off the rails. Finger poke confirmed 17/306. Sensor topped out around 15/270 before coming back down. After I got home from work, I poked again and the readings were off. The sensor said 7.7/140 but the poke said 9.6/175. I calibrated it again at that point because it's been more than 4 hours since I've last eaten and there aren't major fluctuations.

I'm wondering if my pump underbolused for breakfast because the readings were off. It's the only explanation I can think of as to why it went so horribly. I don't usually go above 12/216 on my worst days.

So my question: I usually check once or twice in the first 24hrs of a sensor but after that I trust it. How often do you poke beyond the first 24hrs?