Neither snow, nor rain, nor heat will keep Late Show fans from their destiny inside the Ed Sullivan Theater at show time. Since David Letterman switched networks in August, his show has been receiving about 5,000 ticket requests per week for 400 available seats per day. And when Letterman announced he’d be broadcasting from Los Angeles May 9-13, more than 17,000 pieces of mail poured in. But Late Show fans aren’t content to beg and plead for tickets on postcards: The show’s small ticket office is jammed with 10 donated canned hams, more than 50 suggested Top Ten lists, a wall of cards featuring the cigar-puffing host, an engraved rock that cost two intrepid Pennsylvania viewers $4.91 to mail, and many letters in which viewers express their undying devotion to Dave by sending him their unused Late Night With Conan O’Brien tickets. What does Letterman think of all this viewer mail? ”Dave’s aware of a lot it and is truly flattered,” says writer Bill Scheft. ”It tickles him a lot. He likes strange stuff.” But since Letterman has never visited the mailroom, better to heed the advice of ticket master Janice Penino-Hoffman. ”It doesn’t matter what you send us,” she says. ”Tickets (are mailed out) on a first-come, first-served basis.” And when will Dave return to sender? The average wait for tickets is six months.