ELM GROVE, Wisc. (MarketWatch) -- During times of a financial uncertainty, many people gravitate to the perceived safety of consumer-staples stocks. Among those that have done very well in the post-financial-crisis years are companies that provide everyday household items such as toilet paper, toothpaste, tissues and soaps. Today might not be a good time to add to those holdings, however.

Among arguments in support of investing in consumer staples is that it is a durable business that is less susceptible to recessions. Among the leading companies, all are expanding their reach into emerging markets at some level, providing at least the idea that there is a growth opportunity. In addition, most of these companies pay a dividend that investors equate with income and safety.

As a group, the low-cost Consumer Staples Select Sector SPDR ETF offers access to several companies with core household consumer brands. Among the top holdings are The Procter and Gamble Company Colgate Palmolive and Kimberly Clark which make up nearly 20% of the fund.

The largest of the three companies, Procter & Gamble over the past five years has seen revenue grow from about $79 billion to $83 billion, with a peak of $84 billion last year for a very minimal top-line growth rate. Operating margins peaked a little over 20% in 2008 and 2009 and have fallen to the 17% area this year. Earnings per share likewise have fallen slightly from over $4 per share in 2009 and 2010 to the middle $3 range this year; even though shares outstanding decreased by 200 million (6.8%) since 2009.

Despite the mediocre numbers, Procter and Gamble shares have risen in price from 63 to start 2010 to about 87 today. The increase is almost exclusively due to the expansion of the price-to-earnings multiple up to the current 23 -- a very high number for a low-growth company. It has recently announced plans to make major strategic moves, first by selling its pet-care business earlier in the year, and now spinning out Duracell. It is uncertain how helpful those moves will be.

It is my opinion that too many investors are bidding up shares in P&G due to recent share-price performance and the dividend, which is paying at a rate of nearly 3% right now. I would not be adding to shares of Procter and Gamble at this stage. I would be selling roughly the equivalent of the gains from 2010 to now, or about one-third of holdings. There is a strong case for selling all shares and buying back later when the dividend rate is in the more historically normal 4% range.

Colgate Palmolive is in a similar slow-growth position as Procter, despite having a more streamlined business at the moment. Though revenue has grown comparatively well from the $15 billion to $17 billion in the past five years, operating margins peaked in 2009 at 23.6% and have fallen back to a more normal long-term number of about 20% now. Earnings per share have barely budged; moving from $2.19 in 2009 to $2.38 last year and projecting a bit lower this year; again, despite a net share reduction, this time by 76 million shares (7.7%) since the start of 2010.

Since dipping into the 30s in 2010, Colgate shares have rallied to the current middle 60s. This has driven the dividend down to about 2.2%. The current price-to-earnings ratio is hugely unsustainable at about 29. I would be selling half of my shares in Colgate. There is a strong case for selling all shares and buying back when the dividend rate has climbed to over 4%, which is historically more normal for this slow-growth company. For experienced traders, there is a short opportunity in my opinion.

Kimberly Clark rounds out the group as the smallest of the three major consumer-brands companies at a market cap of $42 billion. Revenue has fluctuated over the past five years, but stand at about $34.4 billion today which is just a hair higher than the $33.6 billion of five years ago. Operating margins have also been more variable, but have expanded on net due to some strategic moves to 15.5% this year. Earnings per share have grown from $4.52 per share to an estimated $5.65 this year, partially due to a decrease in shares of 45 million, or a little over 10%.

Share price for Kimberly has grown from the 60s to over 110 with a price-to-earnings ratio of about 20. Of the three companies discussed, this is the one I would most likely own, though I would be selling about a quarter of shares at these prices and ratios.

While I know it is hard to hear to sell a stock that has done well for you, if you are a shareholder, you must ask yourself the question, if these shares drop 20% or more in coming years due to margin contraction, can I stand it. I can think of no reasons to be a new buyer for those who don't own shares now.

Disclosure: Kirk and certain clients of Bluemound Asset Management do not own shares of any security mentioned. Neither Kirk nor Bluemound clients plan any transactions in the next three trading days. None of the mentioned securities are currently recommended at Kirk's American Resource Boom Letter. Opinions subject to change at any time without notice.