just allow one hour in traffic jam and another 30-40 minutes to airport. Should be fine.
We were there this year & couldnt believe how organised it was, they the close the motorway so all lanes are coming out of the circuit at the end, we waited around for a bit after the race but hardly queued. we have booked all our flights and hotels but has it officially been confirmed for that date yet? keep checking the website but cant book grandstand seats yet!