"James
This isn't always the case. I've won wet races in past where bright red tires were faster only for short periods. Holding the tires at pink/slightly red is almost always quicker over a stint than bright red in my experience. If you hold proper temperature, you'll probably lose time for a bit, but then your opponents will hit the cliff and you'll make up all the time you lost and then some.
I'll second this. I've seen drivers (generally ones who aren't present) who have the maximum push setting start off brilliantly, but as soon as their tires turn bright red it's just a matter of time. It usually takes about a lap or a lap and a half, but by that point their pace drops and they're losing whole seconds per lap. It's like James said. There's a cliff, and eventually they'll hit it.