Does it at least give un an insight into their character and heart?
No, because people can change greatly in 20-30 years -
Peoples motives and aspirations 30 years later can cloud their judgment along with adjusting their integrity.
Furthermore serving in a conflict 20-30 years ago gives one very little "expertise" regarding a current conflict today. Especially when the situations are night and day (regardless if Hagel can't let go of his past to see the truth).
Hagel and McCain both have very narcissistic personalities. In ways this could have served them well at times in the service (and in war)....however it doesn't serve them well (or our Nation) with them in their current roles.