Epicurus denies that:
1. the length of time contributes anything to living happily
I believe that I could agree with this if it's an accurate translation. You can live a "happy" short life or a "happy" long life. The length of the life doesn't necessarily equate to one's overall happiness
Perhaps, but I am not sure there.
I do think Epicurus knew the difference between pleasures that last a short time vs. a long time. But on the other hand, long pleasures are not necessarily the most pleasant. So it really makes a difference how you phrase what it is you are talking about.