While repetition is a good method of learning - repeating the same sentences all the time only reinforces those sentences.
Change them up with differnent subjects and predicates to reinforce the concept being checked expecially in the practice sessions.
Also consider a longer audio tab just to listen to the flow of the language - maybe two or three sentences just for listening about a particular concept.
This is exactly what they are attempting to do. Keep in mind that as you are beginning, there are only a few subjects which you know and have the capacity to remember without knowing any tricks and tips. As you complete more exercises subjects change a lot more, but there is still a fair amount of repetition. I feel there is currently just the right amount of repetition in DuoLingo. Remember that not only the verbs need to be stored in your memory, but the subjects also.