Could have Should have

I could have been their time, It should have been their time, With the kids now in their own time, And retirement giving them the time, To take their time. Instead they are calling time, After all this time, Such a shame when they could have been having the time of their life, Such a shame when they should have been having the time of their life. Instead they are are both having a miserable time, With lots of crying time, With lots of yelling time, Much frustrating time, And even more blaming time. When it could have been their time, When it should have been their time. I wonder if they could go back in time, Would they avoid calling time, By spending more time, Discussing this time.