i think the amount of time you know someone does matter becuase people change as the relationship goes on, your partner might start taking things more seriously and act differently later on than in the beginning when it's all just fun and games...i would say a year is long enough though.
age, to me doesn't matter though...if u love the person, it shouldn't matter how old they are...as long as they're old enough
and no, i wouldn't listen to my parents if they told me to marry or not to marry someone...i love who i love, not who they would like me to love.