Why would you want to? Why does anyone use kboost in the first place? Is there any reason why you want your card to run at 100% all the time even when there is no load? Is there a reason why you want to waste power and heat up your room for no reason? I personally think that kboost is a very pointless feature and do not use it.

Yes, running your card at full speed all the time will reduce its life. By doing so, it is running hotter with more voltage, and therefore life is reduced.

The only real reason for kboost is to make your GPU's run at max for benching. Otherwise you have a short time at the beginning where the GPU is ramping up. But honestly it's such a short time that it doesn't really matter. Like ty_ger07 said, there really isn't a reason to. It just put's extra stress and wear on the GPU and it wastes a lot of energy.