Thanks for tagging me.
The challenge I see right now is there's not much out there that provides a return absent of volatility. Personally I'm buying the small cap value index, at an 11x PE there's only so much room to fall, plus the fed is backstopping the debt issuance right now. That's changed the downside game and it yields 2.5%. IJS is my preferred ticker. I think we'll see a 40% return on that index, but what I can't tell you is will that be in six months or three years and how bad the roller coaster will be in between.
Outside of that, if you want a more conservative approach just split the money between Vanguard Wellesley Income Fund and the Vanguard Wellington Fund. That'll get you 50/50 stocks and bonds with the benefit of some of the best money managers in the world for about a 0.18% expense ratio if you're in the admiral shares. I'd expect a 5-8% return a year in that split with low volatility. I think that's a better choice than just sticking the money in BND right now.
Since you're already FI, you can probably take a little more risk with the money than 1% on a savings account or the 3% you can get in the bond index without much upside.
Regarding going just long term bonds or just mid-long term treasuries, I think the big money in that trade is dead and you get hurt if interest rates change. I don't think rates go up any time soon, so you're signing up for a strategy that, in the words of a great wall street writer..."pays chicken feed with the chance it takes an elephant s***"