A retirement date changes how many years employment income supports your spending, and how long savings need to last. Put both ages beside each other using the same savings, spending and benefit assumptions.
More spending today can change both the years your money supports and what remains later. Compare two spending amounts after tax, keeping the rest of the plan the same.
A saved plan gives you a starting point to return to. A check-in compares the inputs and results already stored, so you can see what changed without rebuilding the plan or silently running another calculation.