Vego & Chimney nailed it.
Most of your sense of taste is in your nose, try holding your nose and eating something and see how it tastes. This is why nothing tastes good if your nose is stopped up. Like smells, if you are tasting the same thing all the time you will lose sensitivity to that taste.
It's like someone who works around strong odors, you just cant smell (taste) them anymore. Walk away from it and come back to it and the smell/taste is still there, you just cant perceive it after awhile.
I rotate between 3-4 flavors all the time so if one starts to lose its punch I go to something else and come back to it later.