Can people with marfan syndrome live long lives?

Varies by severity: People with mild Marfan syndrome symptoms probably live a pretty normal lifespan. Those with severe symptoms can die from heart valve problems, rupture of the aorta, tension pneumothorax, etc..., before they reach old age. Of course, those with moderate symptoms will have a lifespan in between.

Yes, depends: The longevity of someone with Marfan depends on the severity of disease. They can live long if there is no significant heart or other marfan-related conditions.