Wait. You'll need closer to $8 million invested at 2.57% (30 yr current yield) to earn $200,000 a year. And consuming that every year means you'll destroy much of the real value of your hoard over 30 years (you're not reinvesting something to cover inflation). Further putting it all into Treasuries is actually riskier than diversifying across multiple assets - foreign stocks, real estate, etc. If we go into an inflationary period and you're locked into a 30 year at 2.6%, you'll watch your fortune collapse and your stipend's buying power crumble.