Bull markets have a maximum shelf life of five years, and Wall Street may soon approach the end of this one, UBS' Art Cashin told CNBC on Friday.
"It's a little bit of catch-up for 2013," he said on "Squawk on the Street." "We've gone for an awfully long time without a correction. Bull markets tend to have a maximum life of five years. We're getting awfully close to that."
Heightened concerns over emerging market currencies and liquidity flows have made for a jittery Friday on Wall Street, Cashin said, as the Dow dropped 231 points during the morning trading session before halving its losses.
If the S&P 500 drops below 1,770, he added, the markets could see a wave of secondary selling. The S&P has held above that level and had regained some traction by noon.
(Read more: No silver bullet for roaring emerging market beast)
Asked whether January's performance would set the tone for the year, Cashin said investors might see some relief next month when pension flows find their way into the markets.
"The key thing the viewers should take away is that it's a nervous Friday in currencies," he said, "and you want to stay away from 1,770."