A total of 116 stocks in the benchmark S&P 500 Index hit 52-week highs in the past two trading days as the bull market roars to the end of the year.

The S&P 500 SPX, -2.03% registered a closing record high on Monday for the third straight session. The index is up 12% this year and has returned 14% with dividends reinvested. That’s an outsized performance when you consider it dropped 7% from Sept. 20 through Oct. 15.

As shares rise, the index is getting expensive. It now trades for 14.3 times aggregate consensus 2016 earnings estimates (we’re using 2016 because we’re almost through 2014). That’s up from forward multiples of 13.5 a year ago and 11.1 two years ago.

There are many factors pushing the S&P 500 Index to new highs, including improved sales and earnings for many companies, nine straight months of 200,000-plus jobs added to the economy, a flurry of other positive economic reports and historically low interest rates.

The Federal Reserve has ended its “QE3” bond purchases and next year is expected to begin raising the federal funds rate, which has been locked in range of zero to 0.25% since late 2008. But the world is still awash with cash, and stimulus moves by the European Central Bank and China’s central bank last week point the way to a continued flow of money into U.S. investments.

If the Federal Reserve begins raising rates next year, while other central banks are lowing theirs, the U.S. dollar may rise, hurting U.S. exports. This is why Rafferty Capital Markets analyst Richard Bove said last week that the Fed “cannot take actions that will harm trade and lower GDP growth. They know this and they will not push rates higher, in my view.”

That points the way to a continued rise in U.S. stock values, and last week’s central-bank moves were among the themes explored by Avi Gilburt on Monday when he suggested stocks would rise significantly in 2015.

But investors need to be careful because an exuberant rise in stock values based on an over-supply of money, rather than on rising sales and production, could eventually set us up for a nasty pullback.

In the meantime, according to Bove, “it is financial summer and the grasshoppers are playing their songs.” He is also thinking about “when the music ends,” but as we have seen since 2008, predictions of an end to central banks’ stimulus programs have a way of being premature.

Here’s a list of the 15 S&P 500 stocks that hit intraday highs on Monday and trade cheapest to 2016 earnings estimates:

For Navient Corp. NAVI, -4.35% , the total return is from April 17, when the company’s shares opened for trading at $15, after it was spun off from SLM Corp. SLM, -2.95% .

Here are charts for three of the companies listed above, beginning with Apple Inc., which is the most expensive to consensus 2016 EPS estimates, but still trades below the 14.3 forward P/E ratio for the S&P 500:

Aside from a dip in early October, Apple’s chart has been a beauty since May, with the 20-day moving average always above the 50-day average. FactSet

Apple’s stock been on a tear this year, returning 51%, supported by stock buybacks that reduced the average third-quarter diluted share count by 6%. The company boosted third-quarter sales by 11% from a year earlier, while sales per share were up 18%. Net income rose 13%, but earnings per share were up 20%.

Apple is the poster child for the positive benefit of stock repurchases, especially when supported by borrowings at very low interest rates. But for some companies that aren’t growing sales and earnings at such a strong pace, buybacks can actually cover up poor performance.

Shares of Wells Fargo & Co. WFC, -4.73% have returned 22% this year, measuring up quite well against the 6% return for the KBW Bank Index BKX, -4.49% .

Wells Fargo has been the best earnings performer among the “big four” U.S. banks over the past six years. FactSet

Wells Fargo has achieved the strongest and most consistent returns on common equity among the “big four” U.S. banks over the past six years. The company’s ROCE has ranged from 13.86% to 14.09% during the first three quarters and has improved steadily from 10.53% to 13.99% over the past four years.

U.S. Bancorp of Minneapolis, the nation’s seventh-largest bank by total assets, has performed even better, with ROCE ranging from 15.22% to 15.55% this year and from 12.80% to 15.73% over the past four years. But its stock hasn’t performed as well this year, with a return of 12%:

U.S. Bancorp has been among the strongest large-cap U.S. banks through thick and thin. FactSet

Here’s a chart for Dollar Tree Inc. DLTR, -3.22% , which isn’t included in the above list, but hit an intraday high of $67.35 on Monday:

Dollar Tree’s shares soared last Thursday, after the discount retailer announced better-than-expected sales and earnings results. FactSet

The company’s shares are up 19% this year, helped by a particularly strong fourth quarter. But Dollar Tree and its shareholders may find 2015 to be a rather difficult year, assuming it completes its acquisition of Family Dollar Stores Inc. US:FDO, because of the target company’s different and less successful business model and divestitures required for regulatory approval.