While optimistic investors have been keeping the FTSE-100 index dancing above 6,000, a mere 15% below its all-time high, a growing debate is focusing on how long this bear market is going to last.

If I were you, I’d snuggle down somewhere warm, because it’s going to get cold out there.

While the credit crunch isn’t over, the worst of the financial shocks appear to be behind us. So attention is turning to other potential elephant traps.

We have yet to see how far and for how long consumers will shrink their spending. Once the penny-pinching sets in, as it seems to be doing, it is a hard habit to break and will depress many share prices.

The other big factor is the rising price of a wide range of commodities, from oil to gold to wheat. Those trends throw up investment opportunities, but they also raise the costs of every commercial company.

Some see the commodities boom as a bubble that will soon pop. I disagree: India, China and other developing countries will be bidding for scarce resources for decades.

Supply will rise to meet that demand, but I am impressed by an e-mail from Money Week magazine that said: “Since 1792 there have been five major bull markets in commodities. These lasted 23 years, 21 years, 23 years, 18 years and 12 years — an average of 19.4 years. The current bull market began around 2000, so we are eight years in.”

There are no cast-iron laws about how long a boom should last, as circumstances are different every time. Nevertheless, we will be lucky to see prices of raw materials falling in a hurry.

That is one reason why the FTSE 100 has remained so high: a large proportion of it is made up of oil and mining companies making money hand over fist. Take them out of the calculation and you are left with a very sorry picture indeed.

As I report elsewhere(see link), this is a vintage time to be a contrarian investor. I believe 2008 will turn out to be a pivotal year, so boldness and lateral thinking could be a winning combination.

It is not as simple, though, as doing the opposite of everyone else. Plenty of investors, professional and amateur, were burnt buying bank shares late last year before we knew the worst. Other shares are on their back because they may never recover.

Timing is all. Fidelity’s Anthony Bolton, doyen of fund managers, said last week that he expected the bear market to hit bottom either side of Christmas.