I just turned 35. It wasn't very long ago that 35 seemed like a relatively old age. But I'm not old, right?

Then I look around at my life and notice that I have a daughter who is about to turn 2, a hairline that has turned my forehead into a fivehead, and -- most damning of all! -- a minivan. So perhaps it's time for me to start investing like an adult.

I don't have 760 months until retirement
For my daughter's portfolio, I prefer a high-growth investing style with the assumption that if one of four fliers turns into Genentech (NYSE:DNA) or Cisco sometime in the next couple of decades, she'll be filthy rich. If three of the companies go bankrupt along the way, well, live and learn. That's what a long time horizon and a high tolerance for risk will do for you.

But for me, now that I've hit the randomly magical milestone of 35, that might not make so much sense, especially if I hope to retire before my daughter gets married -- and since she's not allowed to date until she's 30, that's a way off.

No, for my portfolio, value investing makes better fiscal sense, at least for a large chunk of my investments. Maybe it's the specter of middle age looming, but I don't feel like I can afford to swing and miss anymore. It's a little sad to hear myself talking so practically, but it makes sense to buy solid, stolid companies that might not wow me with 40% growth estimates by breathless analysts but will assuredly rise in value over time.

Looking over the scorecard of our Motley Fool Inside Value newsletter is hardly as breathtaking as a glance at the Rule Breakers list of recommendations. It's a list of banks and consumer goods conglomerates and companies that make Post-it Notes -- things that everyone already knows everything about -- not mysterious biotechnology companies that might someday develop a winning drug.

The obvious can help you
Bill Mann is one of the smartest analysts here at Fool HQ. He wrote in a recent column that obvious facts cannot help you profit in the stock market. Rather, the key is to find companies that have growth potential that others don't realize.

That's helped Bill in his own small-cap crusade, but when it comes to large caps, I think the obvious can help you a lot.

3M (NYSE:MMM) is an excellent example. The company has a $50 billion market cap, 100 years of innovation under its belt, and, as anyone who watches his company's office supplies arrive knows, very little chance for abject collapse. Plus, the company does well by its shareholders. As Philip Durell wrote in his formal recommendation of the company in his September issue:

3M recently boosted its quarterly dividend from $0.36 to $0.42 a share (up 16.7%), so the stock yields approximately 2.3% going forward. In the past year, the company has repurchased a net 1.35% of shares outstanding, which in my book is another way of returning value to shareholders. Put those percentages together, and 3M yields more than 3% to shareholders. The company is also able to internally fund capital expenditures and its very necessary R&D programs. Over and above this capital allocation, the company has increased its cash hoard from $302 million at the end of 2000 to $2.67 billion at the end of March 2005.

Thrilling? Perhaps not. Smart? Yup. And the stock is down slightly since Philip recommended it, presenting an even better buying opportunity. Slowly, surely, 3M is positioned to reward long-term investors. And I promise 3M isn't going out of business anytime soon.

Value all around
Moreover, if you take a look at recent 52-week-low lists, it's almost a who's who of excellent businesses: Wal-Mart (NYSE:WMT), Costco (NASDAQ:COST), Bristol-Myers Squibb (NYSE:BMY), Gap (NYSE:GPS), and International Paper (NYSE:IP). Some of these companies have short-term risk -- International Paper is being hit hard by energy costs and is undergoing restructuring -- but they don't carry nearly the risk of that pharmaceutical company waiting on positive phase 3 data that could give my daughter a 20-bagger.

This, of course, doesn't mean that I've become a man with a short timeline or total risk aversion. I still (hopefully) have many investing years ahead of me, but it's time I changed my focus. I'm less excited about those high-risk, high-reward fliers with a chance at excellence, focusing instead on proven businesses that generate cash, pay dividends, and offer compelling long-term growth prospects not because of an innovation that might pay off but because the market is selling them at a discount. That's profit with a side of capital preservation. And with a young family and savings accounts for college and retirement piling up, I'm beginning to really respect Warren Buffett's two rules of investing. Rule No. 1: Never lose money. Rule No. 2: Never forget rule No. 1.

Foolish final thoughts
Later today, Philip is going to offer up two new picks that he's confident will increase in value over time. Thus far, his track record is impressive: In the first 13 months of the service, Philip's Inside Value picks are up 5.45%, compared with a relatively flat S&P (up just 0.91%). If you sign up for a free, no-obligation trial today, you'll be among the first to see those picks when they're released at 4 p.m. EST, and you'll have access to all 30 formal recommendations Philip has made since the launch of his service.

When looking to get rich slowly, it's best to invest like an adult.

Roger Friedman is the managing editor of newsletters and the author of Nipple Confusion, Uncoordinated Pooping and Spittle: The Life of a Newborn's Father . He does not own shares of any company mentioned in this article. Costco and Gap are Motley Fool Stock Advisor recommendations. The Motley Fool is investors writing for investors.