I have recently received my Schengen visa and the duration of stay is 11 days valid till 8/24 which would suit the trip schedule I presented to the consulate. I then decided to reschedule my trip as a friend of mine will be joining me so I can now stay for 18 days on the same budget.
My question is can I stay longer than the duration listed in the visa and leave before the 24th ? Will I have to pay any fines ? Is my passport going to be checked every time I'm flying in the Schengen area ?