It's always risky, trying to observe milestones in Philadelphia sports history.

The Eagles unveiled plans yesterday for celebrating their 75th season, showing a beautifully edited video that crackled with images of unforgettable moments and legendary players. It also included a couple of sobering factoids.

Since Bert Bell and Lud Wray paid $2,500 for a new NFL franchise in 1933, the team has played in 11 stadiums and won three championships. That's a profoundly depressing ratio.

The net effect of all that history is to remind you how fleeting every era is. Watching clips of Reggie White and Ron Jaworski and Wilbert Montgomery drove home the reality that we'll soon be looking back on the careers of Donovan McNabb and Brian Dawkins and Brian Westbrook and, yes, Andy Reid.

We know the number of stadiums will hold at 11 for a while. How about the number of championships?

Owner Jeffrey Lurie was emphatic in his belief that the window of opportunity remained open for the franchise under his stewardship to be redefined from "winning team" to "team that won it all."

"We have a franchise quarterback, a terrific nucleus, and terrific veteran leadership," Lurie said. "I always try to analyze where we're at compared to the other teams. . . . I don't think we're anywhere close to the closing of that window."

Lurie's strategy, to hire the right head coach and find the right quarterback, has worked in making the Eagles a perennial playoff team. This off-season, both pillars of that strategy have been in jeopardy: McNabb is rehabbing a major knee injury, and Reid has said he considered walking away from his job after his two oldest sons were arrested in late January.

The Eagles' smooth-sailing ship found itself in rough seas.

"It was very emotionally trying," Lurie said of the Reid family's situation. "I personally feel such compassion for Andy. He's such a gentleman. Not only is he the most successful coach ever for the Eagles, but he's such a nice, warm, genuine man. That's why he's such a successful coach. You don't want to see him suffer from any family troubles."

Lurie said that while Reid took time off to focus on his family, he considered the possibility that his coach wouldn't be back at all.

"You just don't know," Lurie said. "When someone's having a family crisis, you don't know how that will continue. He's a terrific coach, a terrific guy to work with. You always want to give as much support and be as flexible as you can so that he can attack those problems."

And if Reid had decided to step down? Lurie said his overall goal of keeping the team competitive wouldn't have changed.

"None of us are irreplaceable," Lurie said. "I'm certainly not. You have to go forward and make the best decisions you can make if that were to ever happen. He's not going to coach forever. No one's going to play forever."

Which is precisely why it's reasonable to wonder whether this team's chances of winning a Super Bowl are dwindling as time and injury take their toll on McNabb. The Eagles seem confident that their quarterback will be fully recovered, but he'll also turn 31 during the 2007 season. He is closer to the end than the beginning.

"Our challenge is to sustain our success" and not "give in to the idea that, well, we've had so much success for seven or eight years - that window - we now shouldn't expect the best," Lurie said. "We still expect to be better than we've ever been. We expect that of the coaches and the players and everybody else. We want to try to extend it as long as we can."

The team has been agonizingly close for most of this decade. There's no getting around the fact that this era will be viewed as incomplete if there isn't a championship parade sometime before all these players are memories in a video. But there's little chance of that happening if the team doesn't remain competitive year after year.

"If you're good enough to win your division," Lurie said, "and good enough to advance to the final eight or final four of your league - at that stage, you have to try to be the healthiest of that group of teams, if you can. You have to be the luckiest of that group, if you can. You have to get the calls that day. If you can be one of the top teams in the sport, things happen."

Those things haven't conspired to happen often for Philadelphia teams, including the Eagles. If Lurie's two shaken pillars, Reid and McNabb, can come back and change that championship total from three to four, all this history will become a lot easier to celebrate.

Contact columnist Phil Sheridan at 215-854-2844 or psheridan@phillynews.com. Read his recent work at http://go.philly.com/philsheridan.