"All About Tenergy" Butterfly Science

Sorry, but this is a question for all here. How do you identify a dead rubber, meaning how do you know that it is time to change your rubber? I searched on youtube and found pingskills video in this regard. It says when the topsheet of your rubber looses grip then it is time to change. However, I have a different story to tell. I use same variant both forehand and backhand. However, my backhand rubbers is used less as compared to my forehand rubber. Recently, I switched my forehand side with my backhand and O boy...wasn't it a pleasant surprise! I have to put very little effort to loop against heavy backspin. But now if I evaluate my rubbers as per pingskills then they both have excellent grip if I rub a ball across the rubber surface. So, this is where I have a doubt. How do I know if the rubber is dead?

If the rubber feel dead when you play it it's time to change it. Just like you said, you FH was looping like shit but your BH was fine.