"Right." Marty could agree with that first part, marriage was something that should be forever and it shouldn't be something they rushed into because he wanted Savannah to be happy - though that was something he wanted.
What Marty didn't follow was how they were suddenly out of time completely - if he didn't marry her now they were never getting married? "I don't understand what happened, you were fine to wait just three weeks ago and now if we're not getting married today it's not soon enough?" He didn't understand how the jump had been made - not when Savannah had told him she'd be fine to wait, not when she had told him there were certain months he could ask, not when he was supposed to still have time to get used to the idea of getting married before they were suddenly unable to ever get married.