It doesn't take an expert to realize the older players get the more their skills decline. Before the high school influx, most people used to say the age of 30 was someone's prime in the NBA. I think I tend to think of it more today around 28. You'll find your exceptions, guys who age like a fine wine (John Stockton and Steve Nash come to mind) but for the most part after 30, you're on the decline.
So let me go out on the limb on something: I don't think the Celtics as currently constructed will win a championship past this season. I still do believe they will win it all this year. In some ways I think this will parallel the 1970s where they won two titles (74 & 76). They were the best team in the league in 1973 as well but Hondo got injured and that was that.
To win in this league you have to be good and you have to be lucky; there's no two other ways around it. And the same will hold true for this year. The Celtics when healthy are good enough to win it. Then the luck factor comes into play. Will they be able to stay injury free? Your guess is as good as mine. Here's hoping right now the injuries affecting the team are playing their part on the season and this will be over with soon. If it's an ongoing issue (which can certainly be the case with an older team) then the luck part may really hinder the C's chances.
I hope you don't think of me as a "glass half empty typical New England sports fan;" quite the contrary. A three year window of opportunity is how I foresaw this playing out when they acquired KG back in the summer of 2007. The fact that one championship has been won already is outstanding. One more and I'll be ecstatic. But that's gotta happen this year. And don't tell me later that I told you so.