Flying is good for as long as it is what you want to do. When it is no longer what you want to do, don't do it anymore. Some people will fly for a career, others will fly for a shorter period. When it is time to move on, then remember the good flights, try and forget the bad flights and walk.
But be careful: The job is more addictive than it seems. You may find it more difficult than you imagined, slotting back into normal hours and normal life...