Can we keep it simple and state that the answer to the question is: not required (not sure how you would get an increase of 5°C in the time frame between perfo calculation and actual takeoff). If you have time available, you're not doing any harm by recalculating. Just use common sense. Can we agree we don't fly on the limits, but we fly safely around in a world protected by safety margins?
If the question is about "optimum" performance, that's not a question to be discussed on the flightdeck by pilots. Because my initial question would be "optimum what?". Assumed temps were introduced for maintenance purposes. So what are we optimizing? (don't worry, I'm NOT looking for an answer here)
What's the point of a 1kts Vr increment, if 99% of the pilots don't call out the rotate at the exact speed? The world is human. Let's keep it human. Not robotic, nor autistic.