Postal workers' motto calls on them to deliver them to deliver the mail in rain, sleet, and snow. The broad-based S&P 500 is following a similar credo, rising regardless of domestic economic data and political tensions. For skeptics like me, that's an opportunity to see whether companies have earned their current valuations.

Keep in mind that some companies deserve their current valuations. While many oil and gas producers have struggled to adjust their production as commodity prices have vacillated, EOG Resources (NYSE:EOG) has inched ever higher. EOG offers investors attractive assets in the oil-rich Bakken and Permian Basin which gives it the opportunity to sell its assets in Cushing, Okla., or, if the prices are favorable, ship them by rail to Louisiana terminals to pocket the spread between Brent crude and West Texas Intermediate (lower shipping costs). Overall, with its liquids production growing at a phenomenal pace I certainly wouldn't count on any sizable downside from EOG Resources anytime soon.

Still, other companies might deserve a kick in the pants. Here's a look at three that could be worth selling.

Back on the shelf
Starting us off this week is frozen and specialty foods supplier Lancaster Colony (NASDAQ:LANC), which markets its products under the Marzetti, New York, and Sister Schubert's brands.

On the surface most food producers have excelled since the recession as consumer spending has picked up. Food producers have used their branding power and relied on the necessity of food to raise prices and drive margin growth.

In Lancaster Colony's latest quarterly results, released in late January, the company reported a 3% revenue increase to $336 million, a new record, as net income jumped 11% to $39.2 million. The big boost came from strength in its specialty foods business, where sales improved 7% on the heels of new product introductions, while its considerably smaller glassware and candles segment delivered an unimpressive 19% decline in revenue.

Now could be the perfect time to consider selling Lancaster Colony shares, as both its current valuation and outlook simply don't match up.

Lancaster Colony is valued at a whopping 22 times forward earnings in spite of an expected revenue decline this year and modest low-digit revenue growth expectations by Wall Street in fiscal 2015. Furthermore, Lancaster is valued at close to five times book value, which appears incredibly frothy for a company struggling to increase its top line.

The other concern stems from its quarterly results. CEO John Gerlach Jr. noted he was optimistic about the company's prospects for the upcoming quarter, but that he did "anticipate a somewhat challenging third quarter-comparison." Gerlach blamed some of this on the late Easter this year, but I believe it also points to the uncertainty of management as to how well its new product offerings will be received. In sum, Lancaster is easily forgettable with minimal top-line growth prospects and an already pricey valuation.

A rotten tomato
This week's second pick, Marcus Corp. (NYSE:MCS), echoes the first selection in that it's a decent company with a valuation that simply doesn't make sense given its growth prospects.

Marcus Corp. operates 685 movie theater screens and 18 hotels predominantly in the Midwest and north-central United States. As you might imagine, much like Lancaster Colony, the company has seen revenue and profits grow steadily as consumers have begun to spend again with the U.S. economy continuing to find its footing. It also hasn't hurt that a recent surge in comic book-based movies has helped draw moviegoers to the theater. In its third-quarter report, the company recorded a 17% increase in revenue and operating income of $5.7 million, reversing a $0.2 million loss in the year-ago quarter. 

However, the good times may be just about up for Marcus Corp. I have two primary concerns.

The first is that movie quality is bound to decline at some point soon, because there are only so many superhero movies that can be hashed and rehashed before consumers lose interest. Overall, movie ticket sales have been trickling lower since 2002 and are currently tracking their lowest total in more than 20 years, according to Movie theaters have been able to counter this trend with higher ticket prices and beefier margins from food and beverage products, but there will come a time soon where raising prices just doesn't cut the bill.

Second, I have to think that the rollback of the payroll tax in 2013, compounded with higher taxes for upper-income citizens, is going to negatively impact the vacation and lodging industry in 2014. With my personal estimation of fewer gross refunds this year for the American consumer, I suspect Marcus Corp.'s hotel revenue per available room will struggle to grow.

At 19 times forward earnings Marcus Corp. isn't sending readily apparently red flags, but its projected top-line growth rate of just 1% in 2015 makes the company very passable at its current price.

Gone in a flash
Rounding out this week, and sticking with our theme of well-run companies whose valuations simply don't make sense, is flash storage supplier SanDisk (NASDAQ: SNDK).

This series is actually a perfect example of ensuring that you don't fall in love with a stock; I specifically target SanDisk memory cards for my high-powered camera, as I view the brand as the top in the industry. SanDisk also provides flash memory cards for smartphones, tablets, gaming devices, and a number of other electronics.

As you might imagine, the surge in electronic gaming devices and smartphones, coupled with the rebound in the U.S. economy and tech sector, has boosted demand for SanDisk's chips, allowing the company to pay out a dividend and pushing earnings estimates for next year up over $6 per share -- a figure that would be seemingly unfathomable five years ago. If you needed any more evidence of its strength, SanDisk's fourth quarter delivered a profit gain of 52% over the year-ago quarter as its solid-state products continued to outperform.

But, as with the aforementioned companies, there are worrying historical trends that would make me wary of investing in SanDisk after the stock has more than quintupled over the past five years.

My primary concern is the company's flash storage business. While smartphones and gaming device sales are soaring, the industry is becoming more commoditized and more competitive, and margins are slowly trending lower over the long run. While SanDisk can counter some of this commoditization with innovation, this innovative cycle tends to result in ebbs-and-flows in its top and bottom line every few years. Realistically this means that SanDisk's shareholders are merely biding their time until then next downtrend.

Solid-state drives should remain the one stabilizing point for SanDisk given their rapid data transfer capabilities, but even so, they only represented 19% of the company's annual revenue in 2013. While this segment is expected to grow, I doubt it can grow fast enough to stem the negative effects of increasing competition which yields low-cost substitutes.

Although I'm angling for a SanDisk flash or SSD product every time I get the chance, I'm personally suggesting you avoid this naturally cyclical stock until it comes down quite a bit.