hi, i have a few questions about my new MBP : 1) is it safe to run the fans at 5000rpm constantly using smcfancontrol? 2) will it affect the lifespan of the fans? 3) which temperature is optimal for the cpu? is there something like an "optimal" temperature at all? 4) would it be better to use an external cooler instead of "overlocking" the fans? thanks!