Once a class is marked as completed, there is no way to go through it again. Although not a huge issue, it raises a serious question: why add the lifetime option in payment if the content is locked once you go through it? It doesn't make sense.

It should be available, but section with completed classes is collapsed by default and name is stroked out, but it should be still clickable and accessible. However if you set date when it's available then class will not be accessible outside the specified date range.