De-tuning congas -- questions

I'm a bit confused regarding the advice to de-tune congas after each session to prolong skin life. Suppose two players, A & B, have the exact same two congas. Player A tunes his to D and G, player B tunes his to C and F. So player A follows the advice and detunes his congas and they are now sitting at -- let's say, C and F. Player B's congas are already at C and F. Player B should not have to de-tune, right? And if so, then the advice to de-tune only applies to those congas that are tuned high, right? And the next question would be, what is considered high? Clarification appreciated.