You can take them as a calibration exercise. "I don't know" or "Between a week and five centuries" are answers, and the point of asking the question is that some due diligence is likely to yield a better (more discriminating) answer.

Someone who had to pick one of two "basic research problems" to fund, under constraints of finite resources, would need estimates. They can also provide some guidance to answer "How long do we stick with this before going to Plan B?"