I played around with that calculator a bit -- the trouble is that I think that the percentage taxable for SS benefits has changed over the years, but it's possible to get a sense for the implied salaries used for various inputs. For someone who's been making more than 100K and is about to retire now, the present value of the monthly benefit is supposedly around $1,680. This is probably near the maximum benefit amount.
Supposedly the current projections are that the system will be bankrupt in 2042 anyway.
But still I'm interested in knowing whether the benefits change if you stop working much earlier.