Instead, there is now "fundamental support" for decent returns in equities during the next couple of years, according to John Stopford, co-head of multi-asset at Investec Asset Management. He told CNBC on Monday that growth in developed markets is above trend and we are in a "drawn-out economic cycle."
"It's taken time for economies to close output gaps, so (the economic cycle) could go on for awhile longer and if that's the case stocks could continue to rally for awhile longer," he said.
It might not be the first time that the Shiller has warned of hefty valuations but his latest comments come just weeks after a significant selloff for global markets that saw major U.S. benchmarks edge into correction territory.
Shiller did add, however, that it remained impossible to time any potential market fall and stressed that it wasn't clear whether U.S. stocks would react badly to a rate hike, with policymakers from the U.S. Federal Reserve meeting later in the week.
"I'm not looking for any big effect," he said. "It's been talked about for so long, everyone knows that it's coming. It's just not much of a big deal."