Whoa, they've been together all morning. They must really love each other.
This is the first time the woman gets involved in the convo. We assume she's commented on the time, because Wilbur writes, "you say." Up until this the poem has been very one-sided (the speaker's side).
It also seems like they've lost track of time—another indication of having a lot of fun together.
Time flies, and I need not rehearse The rosebuds-theme of centuries of verse. If you must go,
Time flies when you're having fun!
The speaker thinks it's unnecessary to recite the old cliché poetry that compares love and beauty to roses. Because they've spent all that time together without even noticing how much time had actually passed, he feels like that is proof enough that they are in love.
Still, it looks like the lover is getting ready to jet.