60 is relevant because it's inherent to the point they are making in having experienced something that inherently requires having lived through a longer period of time.

Its not uncommon for people to lose interest or find the passion has gone out of things they enjoyed when they were younger, especially in their professional lives where the enjoyment eroded through forced contact with aspects of it that were less enjoyable or contaminated by unpleasant work environments and uninteresting projects.

Having that passion reignited isn't something given to all people.