WHISTLE WHILE YOU WAIT . . .

Those Disney scare ads are . . . well, scary. Moviegoers are being warned that they better see “Snow White” NOW, because “once she leaves, she won’t be back for another generation.”

Since Webster’s tells us the length of a generation is 30 years, well, the prospect of not seeing the 50-year-old Snow White until 2017 left us awfully grumpy.

A spokesman for Disney said the ads are intended to emphasize that while viewers may watch other Disney classics on the Disney Channel or on a VCR, when “Snow White’s” theatrical showings end this summer, it’ll be five to seven years before she returns.

That’s the traditional hiatus Disney gives its animated classics. Disney figures that’s the time it takes for one generation to grow up and go on to other movies while a “new generation of children” is just old enough to buy tickets.

“Snow White” has grossed $350 million since its 1937 premiere. The current reissue has nabbed $42 million.

The spokesman said that Disney’s success with first-run animated features and their “second lives” in merchandising, sequels and home videos has inspired the studio to consider “presenting one animated feature every Christmas.”

“Cinderella,” due in theaters Nov. 20, is next up for her generational appearance.

One project (due Xmas ‘88) is a musical based on “Oliver Twist” (original, no?) featuring a gang of dogs, a cat, original music by Barry Manilow and the voices of Billy Joel and Bette Midler.