Bad enough that Johnny Carson had to retire. Tougher yet--for men, anyway--when Madison Avenue's idea of maturity forced Cheryl Tiegs off magazine covers. Considering all the emphasis on youth in America, it's nice to know a few traditions remain untouched, such as that roomy old reliable, the Ford Aerostar minivan. It's a big minivan with a folksy ambience--a family dinner table on wheels--and except for the welcome tweak here and there, not a lot about the Aerostar has changed in recent years. Except, of course, its life expectancy. Ford was all set to put the Aerostar to sleep a couple years ago, when the front-drive Windstar emerged as the company's slick new family hauler. Understandably, Ford saw little reason to keep a loveable old lug like the Aerostar around. Still, Aerostar's charm then and now is that it possesses some of the broadest shoulders in the marketplace. It's a rear-wheel-drive horse that can haul loads and hold lots of people. Had Ford carried out its plans, families galore would have been as disappointed as a militant majority of Ford dealers, who lobbied hard to keep the Aerostar in the family. The dealers didn't want potential customers heading off to General Motors for Chevy Astros and GMC Safaris, the Aerostar's key competitors. So, here it is again in '96. Big and pleasantly bulky. Long, especially in the long wheelbase model, and offering some of the best legroom of any vehicle this side of a rock star's road bus. But it's also good-looking and pleasant to drive, a maxi minivan that delivers family-solid, meat-and-potatoes service covering a broad range of duties.