My spreadsheet is not set up to solve the problem, "When can I retire?"
It is set up to solve the problem, "How much income can I put in place for a retirement date between November, 2009 and July, 2010, and what do I have to do to make this income consistent with what I will need?" as well as some other related questions.
Working beyond 2010 has not been an option that I would consider since a few months after creating the spreadsheet. I have been working on my spreadsheet since around 2000, so it did allow a 9-10 year timeframe.
I have spent countless hours juggling possible income sources, looking at what various sizes of a fixed immediate lifetime annuity might do for me, for example, correcting the expected rate of growth of my nestegg as time went by and it grew faster than anticipated, and correcting other factors, and trying various scenarios with different inflation, consumption, salary increases, and other factors. Before my house was paid off, I tried various irregular sized lump sum payments, and various times, to see the effect on the balance left.