I can see both sides, life certainly isn't over at 40, and there are a lot of potential experiences ahead.

But the emotion of rewinding to 20 and living it over again would be gone (retaining your memories/knowledge). The sense of accomplishment of graduating school, first job, first loves, etc. The uncertainty of it all doing it the first time lends itself to excitement. The utilitarian benefit of reliving your life would be net positive for personal success but the emotion and excitement would be gone from it.

To pull an awkward analogy, its like saying, would you like to be able to bench press 405lbs at the snap of your fingers. (To the extent someone cares about that.) Great you have the utilitarian benefit of being strong, muscular too, but none of the actual achievement.

Yes there are always more movies, books, vacations, knowledge to be had, but your life is utterly robbed of the achievement of key defining moments of your life that you experience in your teenage years and 20s.