Three years ago, investors received a brutal lesson in why it can be risky for banks or other financial institutions to fund long-term holdings with short-term debt. But could it be time for investors to relearn that concept in relation to sovereign debt?

That is a question hovering over the $14,300bn US Treasuries market as the political fight about US fiscal policy intensifies.

In recent months, the atmosphere in the Treasuries market has been eerily calm, so much so that this week 10-year yields dropped to their lowest level this year.

That is striking, given that the Treasury technically hit the debt ceiling this week (the limit to how many bonds it can legally issue), and could even tip into a technical default in August if Congress fails to reach a deal to raise that debt ceiling by then.

But while it is reassuring to see that investors are continuing to gobble up US debt, even amid this political uncertainty, investors and politicians would do well to look also at what type of debt the US is selling today - and, more importantly, what it has sold in the past.

The issue revolves around the average maturity of the Treasuries market, or how frequently the government needs to sell new bonds to replace expiring ones.

This average maturity is now about 61 months, meaning around a ninth of the stock must be replaced each year.

By the standards of recent US history, this does not look too odd.

Since 1980, the average maturity has moved between 45 and 70 months. In 2008 it fell as low as 48 months, because the US government issued a large quantity of short-term debt to calm the financial markets.

However, when viewed with a wider lens, this US pattern looks unusual and unnerving.

In the UK, for example, the average maturity of sterling government debt is 13 years. While the UK is somewhat extreme in its duration, even in much of continental Europe the maturities are between seven and nine years.

David Fuller's view If US 10-year Treasury Bond yields (historic monthly, weekly & daily) are bottoming out in a lengthy base building phase, as I maintain, the next significant move should be upwards.