That depends on many factors like your study history, language skills in your native language or languages similar to Italian, whether you also use other study material, etc.
As long as you feel like you’re learning something (introducing new concepts or reinforcing past ones) you might as well keep going.
When I used a similar course for other languages, I would keep going for a few lessons even when I felt I wasn’t keeping the pace, then go back about 10 lessons.
However, other people could feel insecure and rather go over the same lesson again the next day. In any case, repetition is useful.
Just don’t repeat until you’re perfect because that’s neither useful nor fun.
