I don't think Carbonneau was fired because he changed the lines too much. If he was, this move by Gainey would be that of a hypocrite, for certain.
No, Carbo was probably fired for a multitude of reasons, with line changing probably not too high up on that list. While his line changes were frustrating, it can not always be said that they were the wrong play.
For example, when he recently put Andrei Kostitsyn back with Saku Koivu it was a good move, even though it meant changing the best line on the team. It was good because Carbonneau was going back to a combination that had been shown to work in the past – perhaps the combination of the season to date.
Critics will claim that Gainey has run out of ideas and is no better than Carbonneau as he places Kovalev on a line with Higgins and Lapierre. While I don't personally like the line either (Lapierre was standing out for me on the wrong side of the equation last game), I don't think that means changing the lines at this point in time is the wrong play.
What's more, this blasted flu (can you believe it? again???) is forcing some changes.
The bigger question for me is whether Gainey will be able to start maximising the assets he has that are working (Koivu, Plekanec, Markov, Higgins in his role) and play the odds a bit better on combinations rather than pulling them out of a hat.
Higgins-Lapierre-Kovalev I can forgive for the moment since Kovalev (Konvalesce) is coming back from injury. I'm much more interested in seeing what he can do to harness Plekanec a little better.