Well, it always depends on what kind of pace you run...
If the whole field starts slowly (mainly 29.1s, 29.2s or even slower) and if I don't start pushing it until lap 30 or sth., the RR tire will turn yellow after 36 or 37 laps and the RF about 5 laps later. I don't know if the LR tire turns yellow or not, I only care about the right sides and start running hard when I can make use of it...for example to catch a draft, to pull away from the cars behind me while they are running 2 wide etc.