I think an answer to an interview question should be considered a mini speech with a intro(tell them what you are going to say), body(say it) and summary(tell them what you said. more than 1 minute but less than 3.

I am a member of a public speaking club and we have session each meeting where everyone gives a 2 minute impromptu speech with no notice. This is very relevant to interviews and has helped me a lot both with confidence and constructing speeches on the fly