Have you heard of Gabriele Pauli? She's a German politician who wants to limit the length of marriage contracts. If a couple is still in love, they could apply for an extension. Otherwise, the marriage contract would expire after seven years.

I'll leave the merits of that proposal to the politicians -- although if it means getting new wedding presents every seven years, I'm all for it. But it did get me wondering about what investing would be like if we were required to dump our portfolios and start over every so often.

Now obviously, the idea of selling your stocks just to buy them right back would just make your broker a lot of money -- and that's not to mention all of the tax headaches. But requiring investors to re-evaluate the stocks they own periodically, to make sure they still love those investments, seems like an idea worth exploring.

As a guy who focuses on drug pipelines, I think the natural time to take a fresh look at developmental-stage drug companies, such as Motley Fool Rule Breakers pick Exelixis (NASDAQ:EXEL), is after each stage of their drugs' clinical trials. If a lead drug flops, that might be a sign to get out, but only a thorough evaluation of the company and how it fits into your portfolio will tell you for sure.

For big pharma, including Johnson & Johnson (NYSE:JNJ), and generic-drug makers, making a decision after every clinical trial or approval doesn't make a whole lot of sense. Teva Pharmaceuticals (NASDAQ:TEVA), for instance, had two approvals in one week. For those companies, it's the trends that count. Continuing to pump out new drugs is what will grow the companies' top line.

For other companies, the times to evaluate your love are a little more regular and predictable. For retail stores, such as Target (NYSE:TGT) and Wal-Mart (NYSE:WMT), you could evaluate your holdings after every monthly sales report, but I'd argue that's probably a little too often. For most companies -- from big ones such as General Electric (NYSE:GE) to much smaller ones such as Oakley (NYSE:OO) -- a perfect time is after each earnings announcement.

It's probably not so important when you evaluate your holdings, as long as you do evaluate them occasionally. If you have any stocks that you think are overvalued, let them go; if you're meant to be together, the stock will find a way back into your heart.

Earnings season can be a bear. Grab a free trial of one of our newsletter services, and let us do some of the work for you. Johnson & Johnson is a selection of the Income Investor newsletter service. Wal-Mart is an Inside Value pick.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.