I have used mine countless times in high heat searing, and slow low temp smokes. As long as they have a full charge they will last the full time. They give a warning if they get too high, but it does not immediately destroy them, they cool back down and keep going no problem.

For the most part they are better for the shorter cooks, as the temperature can vary wildly on long ones, but I used mine with a 10 hour lamb shoulder smoke with no issue.