The benchmark 10-year Treasury yield this week exceeded 5% for the first time in almost three years, hitting the highest since 2007 as oil gained on growing risks to global supplies. While the ascent in yields has dealt pain to investors, they now have an opportunity seen only fleetingly since the global financial crisis — buy now and lock in a roughly 5% annualized return for the next decade or longer.

A net $625 billion poured into US bond mutual funds and exchange-traded funds this year through August, the most for that stretch in Morningstar data going back to 2010. Asset managers including PIMCO and Vanguard expect the pace will accelerate as investors shift into fixed-income from stocks.

"Those are attractive rates for putting money to work, especially when you think about the investor that for the last 15 years or more has been all-in on equities," said Kevin Nicholson at Riverfront Investment Group.

Meanwhile, concerns mount about stresses in private credit, though there's no agreed-upon way to measure default rates. Fitch Ratings put the default rate at a record 6.3%, yet weighed by loan size, defaults remain below **1%", said Lotfi Karoui at Pimco.