Properly stored, shredded cheddar cheese will maintain best quality for about 8 months, but will remain safe beyond that time. The best way is to smell and look at the cheese: if cheese develops an off odor, flavor or appearance, it should be discarded, if mold appears, discard all of the shredded cheddar cheese.
No. Blackbeard did not eat Whitebeard. He ate Withebeard's devil fruit, hence gaining power of quake-quake fruit.
How Did Blackbeard Acquire His Second Devil Fruit? After Blackbeard wrapped the black cloth around Whitebeard, he did something in order to acquire the Gura Gura no Mi. In essence, this isn't actually having two Devil Fruit powers, but instead a copy of the earthquake power.