One of the strong points of the Stack Exchange system is that the best answer, as judged by the community, floats to the top. And a person seeking an answer to the question should be able to get all that is required from the topmost answer.
So there's nothing wrong if answers are edited often, even if it is to incorporate material, with acknowledgement if necessary, from other answers.
I think editing answers other than the topmost and usually the accepted answer may often, but certainly not always, not be worth the effort.