5 years is also a rather pessimistic number, but it makes for a good story I guess if you want to build a case against it. Most mainline manufacturers recommend a change every 100,000 miles or so. Some include a time interval as well; Honda figures 15,000 miles/year, and their timing belt change interval is 105,000 miles or every 7 years. An independent shop can do the job for $500-600. You can do it yourself for half of that.
And as this thread correctly points out, a timing chain is not a guarantee of reliability. In general, timing chain systems are designed well. But they aren't always...