Seniors heading out for skiing vacations this winter are going to have more trouble finding deals.

The reason offers a glimpse into the aging of an active generation: There are now so many seniors zooming down the slopes, resorts have less of an incentive to try to lure them. Indeed, the numbers of fit, affluent seniors are making the senior discount, long sacred throughout the travel industry, a rarity in highly athletic sports like skiing and hiking.

While it's difficult to tell how many senior-citizen skiers there are, visitors aged 45 and older made up 31% of total ski-resort business in the last season, up from 21% seven years ago, according to a report by the National Ski Areas Association, a Lakewood, Colo., industry group. As a result, ski resorts across the country are boosting the age threshold for senior discounts. They say they can't afford to give up a growing source of revenue as the average age of skiers keeps moving up.

Skiers aged 70 and older used to enjoy free skiing at Hunter Mountain in New York's Catskill Mountains. Starting this season, they'll be charged $79 for an unrestricted season pass, while seniors over 65 pay $599. At Vail Resorts Inc., which operates four resorts in Colorado and one in California, the 70-and-older set pays $599 for a season pass, about $1,000 less than younger skiers. Free skiing for these customers was eliminated in 1999. "There's nothing free for them anymore," says Vail spokeswoman Kelly Ladyga.

And skiing is no longer free for the 70-plus crowd at Park City Mountain Resort in Park City, Utah. Owing to increased demand, the resort this season for the first time began charging septuagenarians $249 for an unrestricted season pass -- 75% off the regular adult price. For seniors 65 and older, daily lift tickets cost $45.

Snowboarding has drawn a younger crowd to the slopes, but winter-sports resorts haven't been able to shake a demographic trend toward older customers. Last winter, the median age of ski and snowboard participants was 36, up from 32 in 1997-98, according to a report by the NSAA. At the same time, advances in ski equipment, such as shaped skis and more comfortable ski boots, as well as improved trail grooming, have made it easier for people to ski well into their seventh and eighth decades.

Most seniors and their advocates seem to be accepting the stingier discounts without complaints. "There are getting to be many of us that are far more active than seniors used to be, so there are less and less discounts out there," says Linda Ginsberg, who took up skiing six years ago after moving to the Colorado Rockies from Chicago. Since then, the 61-year-old, who skis at Vail Resorts' Breckenridge resort and works part-time in the lift ticket office, is taking the changes in stride.

Many seniors who ski are among the sport's most frequent participants. At Vail Resorts, senior pass holders are three times as likely to ski 100 or more days per season than any other pass holder. Last year, nearly 4,000 senior passes were sold by the resort, a 33% increase from two years earlier.

Some resorts are keeping their discounts in place. At Intrawest Corp.'s flagship Whistler Blackcomb resort outside Vancouver, British Columbia, skiers have long had a discount starting at 65. "The ski industry overall is still pretty flat, so we don't want to lose skiers once they turn 65," says Whistler's Christina Moore. Skiers 75 and older pay about $85 for an unrestricted season pass while it costs the 65-to-74-year-old crowd about $565. The regular adult price is $1,141.

At Intrawest's Mammoth Mountain in California, skiers ages 65 to 79 can purchase an unrestricted seasonlong "Gold Pass" for $650, discounted from the $1,300 that other adults pay. The passes are free for skiers age 80 and older.

In Sun Valley, Idaho, skiers 65 and older are still eligible for daily discounts. A resort spokesman says they don't break down discounted ticket use by ages, so it's impossible to track how many take advantage of the lower prices.

Richard Lambert Jr. is a youthful 35, but he helps his 76-year-old father run the 70+ Ski Club, based in upstate New York. Mr. Lambert says that small independent resorts -- not the big operators -- generally offer the best discounts.

At family-owned Mount Baker outside Bellingham, Wash., for instance, discounted prices are still available for skiers aged 60 and above. Once a skier hits 70, $25 buys an unrestricted pass. Skiiers who are 60 and older made up about 8% of all season pass holders at the seven-chairlift resort last year, says spokeswoman Gwyn Howat.

At Alta Ski Area, 25 miles southeast of Salt Lake City, octogenarians ski free and ride the resort's shuttle buses for no charge. Until five years ago, there was one price for everyone else. Now, skiers 65 to 79 get a $400 discount on unrestricted season passes.

For avid senior skiers, it's tougher than ever to find a good deal. But that doesn't mean there aren't deals out there. There are also opportunities for seniors to work as resort greeters and mountain guides.

"We know there are ways to work the system," says Ms. Ginsberg, the Colorado skier. "After all, many of us are retired, so we have the time to figure it out."