Should the US sell ultra-long (100 year) bonds?

The longest bond issued by the US Treasury has a maturity of 30 years and the average maturity of outstanding debt is 5 years (59 months).

However, the TBAC (Treasury Borrowing Advisory Committee) has discussed selling "ultra-long" maturity bonds with up to 100 year maturity, to exploit low borrowing costs. Who would invest in such low-yielding paper? It is argued long-term investors like pension funds and insurance companies...but wouldn't they also want to see a return?

France, China and the UK have sold 50 year debt.

The benefits to the US Treasury would also include diversification of its investor base beyond the largest investors, foreign central banks, thus "reducing funding risk".

In Lehman news, it has been reported that Bernanke on 14 Sept 2008 wrote in an email: $12bn plus Fed liquidity support would not be enough (to keep Lehman afloat). On 9 Sept 2008, the Liquidation Gameplan was distributed, highlighting: "Lehman is bigger and more global than Bear Stearns".