Except for Trump who wanted him as his VP no one in the administration or even the transition team liked Flynn. Which is why no one covered for him, he was cast out almost immediately.
The way I see it, Flynn would've been back to writing op-eds right now if he had kept his job and would've been fired or left within 3 months.
The problems that others faced like Trump not giving a shit during the first 6 months of his presidency and the Priebus/Banon/Kushner civil war would've pushed out Flynn.
Just like when Bolton joined and the only thing Trump ever did was tell everyone how stupid his ideas were and how he wanted to start wars with everybody.
With all positions about three things happened
1) Trump didn't or doesn't care so you could do what you wanted (Rex, Scott, Perry, Carson)
2) Trump cared so Ivanka and Jared were your new boss (Priebus, Mnuchin, Wilbur)
3) Trump thought you did a good job so you got promoted to do all the jobs Jared didn't want until you imploded (Kelly, Mulvaney, Pompeo)
And then there's the characters he keeps around for TV and drama like Kelyanne.