"I don't expect these to last out the day," said Paul Young, waving at a stack of pre-Castro Havana cigars on the shelf of his J-R Tobacco store on 17th Street between K and L.

There were 6,000 of them when he opened the sale yesterday, and the price would make Jack Benny rub his hands.

The five-inch Brevitas go for $135 a box of 50, the tapered three-inch Farachitos for $80 per 100. They come in great old cedar boxes with weathered Flor de Farach labels, collectors' treasures in themselves.

These are the last batch of the 200,000 Flor de Farachs, made in 1958, that surfaced more than a year ago in New York. They had been shipped out of Cuba by a farsighted Spanish dealer but impounded by the Spanish government at Castro's request a year later. The dealer died while his case was still in litigation, and eventually the cigars were bought by J-R, a major tobacco importer, and auctioned off.

Paul and David Young, the retired restaurateurs who opened their J-R outlet last year (with the help of their veteran maitre d', Emanuel Anagnostiadis), picked up a few shelf loads for sale at popular prices. Most of the original cache was sold to J-R retailers.

"We could have charged eight or nine dollars apiece," said David Young, "but this is more fun."

Young, who doesn't smoke, has made himself an expert on cigars just as he was an expert on wines in his restaurant days. He vouches for the 27-year-old Havanas.

A sample Farachito felt like a true Havana, all right -- good and hard, solidly packed, with a faint, crisp crackle when rolled between finger and thumb, yet easy on the draw. It smoked sweet and smooth, was never sharp on the tongue, and "didn't stink at all," according to the woman at the next desk.

Most buyers at the cigar store, which is one big humidor, were asking for a single box. This was fine with the Youngs, who said they would rather spread the good word than simply move the cigars into somebody else's humidor.

"Even the modern Havanas don't seem to have the classic quality of the old ones," said Paul Young. "Castro planted all those fields in sugar cane, and it takes years to get the soil back into the right condition for tobacco."

Before you know it, all these antiques will be gone, and the smell of a true vintage Havana will be just a memory on this planet. Ah well. A good cigar, as the cryptic adage goes, is a smoke.