Frozen Shredded Cheese can keep in the freezer safely for up to a year although after 6 months the shredded cheese may not be as fresh and the texture may change.
But the shredded cheese will still be safe to eat after a year in the freezer.
I buy shredded cheese on sale in the store and then freeze the shredded cheese and use it within a year for cooking things such as casserole or melting the shredded cheese on chili dogs etc and the taste is not noticeable.
I prefer to use fresh shredded cheese though in salads or other coll dishes but for cooked dishes the shredded cheese being frozen and then thawed out is perfectly fine.