I pumped for 6 1/2 months, and then fed
milk from the freezer for 2 more months. That
milk that she was getting at 7 and 8 months was produced when she was a newborn-6 months. It was perfectly fine. While the composition of milk does change, it is still great for baby- even milk from a different time and frozen still has more beneficial properties than formula.
This little one will be getting frozen milk when I quit pumping.