How does Lennox mature throughout the play?

When Lennox first appears in Act II, Scene 3 of Macbeth, he is represented as an innocent, naive youth. He indicates that he is young and inexperienced when he tells Macbeth, regarding the stormy night:
My young remembrance cannot parallel
A fellow to it.
Lennox is nervous when he finds himself alone with the grim and strangely silent Macbeth, who is dreading the moment when Macduff discovers Duncan's body and raises an outcry. The young lad tries to find something to talk about to ease the silence, so he talks about the weather.
The night has been unruly. Where we lay,
Our chimneys were blown down, and, as they say,
Lamentings heard i’ the air, strange screams of death,
And prophesying, with accents terrible,
Of dire combustion and confused events
New hatch'd to the woeful time. The obscure bird
Clamor'd the livelong night. Some say the earth
Was feverous and did shake.
Everything about Lennox shows that he is young, inexperienced, and naive. Yet in Act III, Scene 6, he seems to have done a lot of growing up in a very short time. Shakespeare is using Lennox's speech to convey a great deal of information, but also to show how the tyrannical reign of Macbeth has affected the entire population. The change that has taken place in Lennox is symbolic of the change that has taken place in the Scottish people. They all suspect that Macbeth may have killed King Duncan and had Banquo ambushed. Lennox has become hardened, worldly, wise, cynical, cautious, and disillusioned—a far cry from the young man who came with Macduff to wake the murdered king.
My former speeches have but hit your thoughts,
Which can interpret farther: only I say
Things have been strangely borne. The gracious Duncan
Was pitied of Macbeth: Marry, he was dead.
And the right valiant Banquo walk'd too late,
Whom, you may say, if't please you, Fleance kill'd,
For Fleance fled. Men must not walk too late.
Who cannot want the thought, how monstrous
It was for Malcolm and for Donalbain
To kill their gracious father? Damned fact!
How it did grieve Macbeth! Did he not straight,
In pious rage, the two delinquents tear,
That were the slaves of drink and thralls of sleep?
Was not that nobly done? Ay, and wisely too,
For ’twould have anger'd any heart alive
To hear the men deny't. So that, I say,
He has borne all things well; and I do think
That, had he Duncan's sons under his key—
As, an't please heaven, he shall not—they should find
What ’twere to kill a father; so should Fleance.
But, peace! For from broad words, and ’cause he fail'd
His presence at the tyrant's feast.
Lennox has learned how to use innuendo and double entendre. A good example of his sophistication is to be seen in these lines:
And the right valiant Banquo walk'd too late,
Whom, you may say, if't please you, Fleance kill'd,
For Fleance fled.
He is alluding to the fact that Macbeth was able to pin Duncan's murder on Malcolm and Donalbain because they fled for their lives. Fleance, of course, did the same thing when his father was being murdered. The young lad might have stayed to try to help his father, but Banquo cried out:
O, treachery! Fly, good Fleance, fly, fly, fly!
From Lennox's words and insinuations, we can picture the reign of terror he has lived through in recent years, with executions, confiscations, disappearances, spies everywhere, troops of horsemen riding in all directions on mysterious errands. Meanwhile, the tyrant grows more disturbed and vindictive inside his gloomy castle.