NEW YORK (CNN/Money) - Even though Home Depot nailed its latest quarter, investors are going to keep on worrying that its latest successes will be only fleeting. Maybe they shouldn't.

The do-it-yourself chain, the nation's largest retailer after Wal-Mart, said Tuesday that it earned 50 cents a share in the quarter ended Oct. 31. That was a four cents ahead of the consensus estimate of analysts polled by First Call and a dime better than a year ago.

Sales, at $16.6 billion, were better than the $16.3 billion that the analysts expected. Home Depot also boosted its full year guidance.

The worry, however, is that much of Home Depot's newfound success is due to the mortgage refinancing frenzy that took hold in the spring and summer, when rates crashed to 40 year lows. And now that the boom is over, Home Depot's prospects are going to fade.

A Fed study of the 1998-1999 refinancing boom showed that when homeowners take cash out of their homes when they refinance, about a third of that cash goes into home improvement. Which makes sense -- when your home has served you so well, it makes sense to fix it up and increase its overall value. Particularly in a time of appreciating real estate values.

But the Credit Suisse First Boston strategist Paddy Jilek points out that this version of the world may not square with the facts.

According to his calculations, in 2002 home owners extracted $685 billion in home equity through mortgage refinancing, loans on second homes and home turnover. That was up from $514 billion in 2001. If a third of that money got spent on fixing up the old home, home improvement sales would have soared.

But, as any investor who held either Home Depot or its big rival, Lowe's, at the time could tell you, sales weren't soaring. Commerce Department statistics tell the same tale.

Shifting through the statistics, Jilek also found that although personal spending has been growing faster than income, that growth rate difference can be explained away entirely away by the drop in tax rates -- spending and after-tax income are growing in line with each other. In other words, the idea that Americans have only been keeping up spending by giving up equity in their homes may not be true.

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So where did the money go? Jilek points out that credit card balances have, in recent years, been growing more slowly than ever before. That suggests that households have been using mortgage debt to pay off high-interest rate debt. Meanwhile, checking deposit growth has grown sharply over the past three years, suggesting households are increasing their precautionary savings.

Jilek admits he is genuinely puzzled by what he found -- the statistics just don't match the anecdotal evidence of spendthrift households we're constantly confronted with. But potentially the idea that outfits like Home Depot are about to see sales growth slow because of a fading refinance boom just doesn't hold water. And potentially the idea that consumer spending is about to lag behind overall economic growth isn't right either.