Top strategist Ed Yardeni thinks it could be a while before we see the end of this economic expansion — and by extension the bull market. But he also says that very few stocks are cheap anymore.

“We’re well into the expansion phase. Real GDP now exceeds its previous peak,” Yardeni tells ETF.com. “What is unusual is that, this far into the business expansion, inflation remains extraordinarily low and interest rates remain extraordinarily low. The conclusion is that this business cycle expansion is likely to last much longer than average, in which case we’re probably looking at a secular bull market for stocks; in other words, one that can last for a few more years.”

Yardeni says the rapidly rising dollar “certainly is a challenge for earnings growth,” but he doesn’t think it will lead to a bear market. The next bear will occur because of a recession, he says.

Yardeni also says the market has held up well in the face of potential interest rate hikes. “But the main problem in the market is valuation,” he says. “Nothing’s cheap. There’s not very much left that’s cheap; it’s all been picked over. P/E’s are historically high. Some sideways action is warranted, and that’s been demonstrated of late with the up-and-down volatility we’ve seen. And that might last a while, maybe through the summer. The market needs some time to get comfortable with normalization by the Fed. And time is necessary to let earnings catch up with rather inflated valuations.”