Warren Buffett, the 75-year-old billionaire investor and chairman of insurance and industrial conglomerate Berkshire Hathaway (BRK) Monday said investors shouldn't expect him to retire any time soon.

He also said they can expect market returns of 6 to 8 percent a year, and reiterated that the dollar will weaken over time.

Buffett earlier this month, in his annual letter to Berkshire shareholders, said the board had chosen a successor, though he declined to name the person or specify when the handover will occur. On Monday Buffett said it will be "some time" before he retires.

"I hope it isn't too soon," Buffett said from the floor of the New York Stock Exchange, where he rang the opening bell to mark his recent purchase of press release-publisher Business Wire.

Buffett said he broached the succession issue in the letter because so many investors were asking about it.

"I've got a little way to go before I retire," Buffett said. "It could be some time."

Buffett, whose stake in Berkshire has helped make him the second-richest man in the United States, joked, "I can't afford to give up the job. I need the money."

The so-called Oracle of Omaha also reaffirmed his views on the U.S. dollar, which he expects will weaken "over time" due to U.S. fiscal policies. Meanwhile stock market returns, he added, should remain modest relative to the out-sized performance of the 1990s.

"I don't expect any enormous returns at all, either for Berkshire or the market," Buffett said. "Overall, 6 to 8 percent is what I think people can expect."