CLINTON AND JANET RENO may be on Hollywood’s case these days about violence, but from the onscreen evidence this season, Dan Quayle may have had more sway over executives and producers at the studios a year ago than anyone could have suspected at the time.Snap Quiz: What do Jack Lemmon, Richard Harris, Beethoven and Dana Carvey have in common? Answer: They’re the only guys who get it on in any of the new Christmas films. Wrapping up my viewing of the year-end releases, I was wondering why I wasn’t feeling all warm and passionate about the holidays when I realized that none of the films released in the second half of November and all of December have any sex scenes in them. Really, hardly any at all. Not that the Christmas season should be, or ever has been, loaded up with amorous antics. But given that romance has been an even more dependable staple of movies than has violence through the years, you would think that somewhere in the course of the 20-odd big commercial films now entering the marketplace, people would occasionally be inclined to give someone more than a feel-good hug or a peck on the cheek. The New Puritanism was supposed to have arrived some years back when Ronald Reagan, Jerry Falwell and the AIDS epidemic were all encouraging people to keep things zipped up. But no, it’s in the era of Clinton, Madonna’s “Girlie Show,” the Packwood scandal and an errant Michael Jackson that everyone is getting squeaky clean and taking up family values when the VP who made that a dirty phrase is no longer here to kick around. THIS CHRISTMAS WILL BE a field day for socio-sexologists bent on defining our culture on the basis of our films. In the only pictures that even go so far as to suggest sexual relationships, the characters are either decades apart in age — Lemmon and Ann-Margret in “Grumpy Old Men,” Anthony Hopkins and Debra Winger in “Shadowlands,” Johnny Depp and Mary Steenburgen in “What’s Eating Gilbert Grape”; both getting up there — Harris and Shirley MacLaine in “Wrestling Ernest Hemingway”; indulging in pure fantasy — Carvey losing his virginity to Kim Basinger in “Wayne’s World 2″; or not even human, such as the dogs in “Beethoven’s 2nd.” Not only that, but the reticence displayed in the scenes themselves is quite extraordinary. In “Shadowlands,” in which Hopkins plays an aging and presumably virginal British don and writer to Winger’s feisty American divorced poet, the discretion is so extreme that you really can’t tell if they actually have sex or not, even though they get married. It was like watching an MGM-British production from 1938. Although the sack action is clearly stated in “Grumpy” and “Wrestling,” it’s shown discreetly. Depp and Steenburgen take a kitchen tumble in “Gilbert Grape,” but nothing more than PG-13 allows. Carvey finally losing his cherry in “Wayne’s World 2″ is also safely covered by that rating, so it is left to Beethoven to prove himself the stud of the Christmas season by siring four pups, albeit safely offscreen. OTHERWISE, IT’S A PRETTY BARREN landscape out there this winter. Granted, Hiep Thi Le has her share of sex in “Heaven and Earth,” but it is virtually all of the unwanted, degrading variety when she’s in Vietnam. Even when she hooks up with Tommy Lee Jones, it all comes to no good. Will Smith is caught in bed with a street hustler who romps around nude for a minute in “Six Degrees of Separation,” but one of the chief flaws of “Philadelphia” is that we never see anything significant regarding Tom Hanks and Antonio Banderas’ intimate life. Even some of filmdom’s most attractive leading players remain chaste this season. After keeping a lid on his passion for Michelle Pfeiffer in “The Age of Innocence,” Daniel Day-Lewis has to spend many sexless years in prison in the forthcoming “In the Name of the Father.” Just out of the pen in “A Perfect World ,” Kevin Costner would rather smoke and drive around Texas than hook up with a lusty waitress. Liam Neeson’s womanizing in “Schindler’s List” is more suggested than shown, and whatever goes on between Julia Roberts and Sam Shepard and, later, Denzel Washington in “The Pelican Brief” is kept behind closed doors. As for “Mrs. Doubtfire,” well, maybe in the sequel Robin Williams can play a dual role as an older man with a Mary Poppins complex. IF THE CHARACTERS in this season’s films aren’t making much whoopee, they are also taking their own sweet time about it. In case you’ve been suspecting that your average Hollywood film is longer than ever, you’re absolutely right. Last Christmas, most of the prestigious releases ran well over two hours, and the trend continues with a vengeance a year later. Looking at the 26 films from major distributors that have been reviewed in Variety since Nov. 1 (including a few upcoming), the average running time is 116 minutes. If one were to include the previously reviewed, but currently in release “Gettysburg,”"Farewell My Concubine” and “Germinal,” the average would be significantly higher. The longest film this season, of course, is “Schindler, ” at 195 minutes, while Universal also released the shortest, “We’re Back: A Dinosaur’s Story,” at 72 minutes. The average for the 25 November-December films 10 years ago was 106 minutes, a minute shorter than it was in 1973. In 1963, the average duration of the 17 Christmas films was 114 minutes, close to this year’s figure, but due only to the inordinate length of “It’s a Mad Mad Mad Mad World” and “America, America.” Prior to that, Hollywood films were much shorter indeed. In 1953, the November-December releases ran an average 87 minutes; in 1943, is was 84 minutes; and in 1933, early in the sound era, the average Christmas film was 72 minutes. And no sex scenes.