Bias died in 1986. Bird played his last game in 1992. Just a silly argument to make. Lewis was obviously different as he was just entering his prime, but Reggie Lewis was not ever going to be a franchise player. He was very good and could have been a solid 2/3 type option, but no team with him as its best player was ever going to win a title. Bird should have been traded some time during the 89-90 season or the 90-91 season (after he was back and healthy from his injured 88-89 season). It was clear at that point Boston wasn't going to win a title with him as the focal point any more and he still would have had at least decent value in a trade. The same is true of Parish and McHale as well (and they played a bit longer so you could have moved them a bit later).
This is probably a bit earlier than I would have wanted to move these guys (especially Bird) but this is what Ainge said was on the table in 1988 (had to be 87-88 season since Stipanovich was in the deal).
Ainge said the Pacers wanted to acquire Bird in 1988 for a package that included Chuck Person, Herb Williams and Steve Stipanovich. Boston also could have moved McHale to the Mavericks for Detlef Schrempf and Sam Perkins, according to Ainge.
Read More: http://sportsillustrated.cnn.com/2011/writers/ian_thomsen/01/25/celtics.notes/index.html#ixzz2aYJwxTwL
Not a huge fan of the Bird trade given this was before his last major injury, but Boston absolutely should have moved McHale in that trade. Schrempf and Perkins paired with Reggie would have been a nice younger front line to build around and even by 87-88 McHale was fading. That said I can get why you don't move them during the 87-88 season, but a year or two later, there really is no excuse. They needed to be moved. They were injured and far from the players they once were and both had a lot of value still to a contending team.
You don't move them in '88 because they were in the Finals in '87, and were the best team ever in '86.
By '90 or '91, though, it was getting to be a team of hope and dreams, much like our last few seasons. McHale and Bird each had their major injuries (foot/back) by then. I don't think the deals that were available in '88 were available in '90-91.
At that point, is it worth trading them for miscellaneous pieces and picks, or maintaining the loyalty and legacy that matters so much still to Larry?
Oh, and continuing to sell out of season tickets, season after season...