Five years into a bull market, Byron Wien doesn't see a top in sight. In fact, the vice chairman of Blackstone Advisory Partners says that there's still plenty of time to buy stocks.

"I think the market's going to flutter around a little bit here in the first half, but I think it's going to be relatively strong in the second half, and I think this year is going to end up surprising people favorably," Wien said on Tuesday's episode of "Futures Now."

(Read more: Stocks in 'euphoria mode': Strategist)

Wien says that stocks remain reasonably valued, and continued economic growth will boost corporate earnings.

GDP growth has been "hovering around 2 percent," but a look at "early encouraging signs" like railcar loadings and bank loans convinces Wien that "the economy could head toward 3 percent. That could be very good for earnings. I think earnings have been cut too far by analysts. I think earnings are going to be better than expected."

As the earnings outlook improves, "the market is going to go higher," Wien predicted.

For investors who aren't convinced that the economy is gaining ground, Wien points to another reason to get in: Stocks are still relatively cheap.

"Look at valuation. The market is selling just slightly above the long-term historical mean, or median. So stocks aren't expensive," Wien said. "You would think five years into the recovery, with the market having gone up from 666 to 1,850, that the market would be overvalued. But it isn't! It's reasonably valued. And maybe somewhat overbought here. But it is not overvalued here."

(Read more: Stocks may be at record highs—but so are earnings)

Wien stands by the forecast he made at the beginning of the year, which is that by the end of 2014, the would return a total of 20 percent to investors.

He cautions, however, that "if the market is up 20 percent, then valuations could get to be extreme. And that might be a sign of the top."

—By CNBC's Alex Rosenberg. Follow him on Twitter: @CNBCAlex.

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