The FSPS is deliberately back-loaded — and the difference between leaving at year 15 and year 20 isn't five-twentieths of a pension, it's most of the pension. Here's what a voluntary early departure really forfeits: the 1.7% multiplier, the annuity supplement, and retiree FEHB — and how to run the break-even math against a private-sector offer.
You can spend three years at post without setting foot in your "home" state — and that state may still tax every dollar of your salary. Or none of it. The difference is domicile, and most people drift into it instead of choosing it.