Tour of Duty, Good Guys, Bad Guys, and the End of Time

My sons listened to the Rolling Stones', "Paint it Black," this evening.  My favorite Stones song for sure.  Tonight, I told them it reminded me of the (awesome) TV show, "Tour of Duty" https://www.youtube.com/watch?v=0z6fcd--354

We then watched the opening sequence of Tour of Duty and then Sam asked:

(Sam): Daddy, can we listen to that again?

Me: No, it's time for bed.  We've listened to that twice already.

S: Can we watch that show then?

M: No.  It has too many bad guys in it [i.e., too much violence for a five-year-old].

S: Daddy, did all those bad guys die?

M: No.

S: How many died?

M: I don't know, but not all of them. It's time for bed.

S: But how many?

M: Not all of them.

S: Daddy. Are there still bad guys?

M: Yes, there are still bad guys, Sam.  There will always be bad guys.  Until the end of time there will be bad guys.  BUT there will ALWAYS be good guys fighting against the bad guys.

S: Can I be one of the good guys?  And when is the end of time?