“American Idol” (7 p.m., Fox) wraps up its fourth season with a two-hour spectacle that will seem 90 minutes too long.

But everything about “Idol” is outsized. It’s watched by tens of millions of viewers who use their cell phones to root for their favorites. Week after week, host Ryan Seacrest claims that 20 or 30 or 40 million have phoned in their vote. Few contests outside of presidential elections receive as many votes.

But what happens when the show is over and the phones stop ringing? What kind of numbers do past stars still attract? To measure the enduring popularity of “Idols” past, I turned to eBay, the world’s most ruthlessly efficient garage sale. I found plenty of “Idol” ephemera, but the demand was hardly staggering.

It took just a few clicks to discover a used copy of “Free Yourself,” the CD by last year’s “Idol” winner, Fantasia. It attracted just one bidder and sold for $5 plus shipping. The “Soulful” CD by Ruben Studdard was more popular: It attracted three bids, but sold for a mere $1.75. A copy of Clay Aiken’s “Measure of a Man,” with the asking price of $1.99, attracted no bids at all. But to be fair, a Clay Aiken picture bracelet got two bids and went for $10.45.

The lesson here is that even “Idol” fame is fleeting, subject to the cruel arithmetic of fan attention span and the savage law of supply and demand. Perhaps that’s why, on a show that seems to specialize in ’70s pop ditties, we’ve never heard potential “Idol” stars belt out the Jerry Reed lyrics, “When you’re hot, you’re hot/ And when you’re not, you’re not.”

For the record, Bo will probably win. The judges have been stacking the deck for him for the past month or so.

Tonight’s other highlights

¢ Scheduled on “60 Minutes” (7 p.m., CBS): Charges of sex abuse by a priest in Springfield, Mass.; travel secrets; a conversation with a mind reader.

¢ A promiscuous lawyer perishes on “Law & Order” (7 p.m., NBC).

¢ The raft contingent has a strange encounter as the islanders contend with the hatch on the two-hour season finale of “Lost” (7 p.m., ABC).

¢ John Travolta and Halle Berry star in the 2001 thriller “Swordfish” (7 p.m., UPN).

¢ A world in peril on the season finale of “Alias” (9 p.m., ABC).