Many films on Kanopy have a 48 or 72 hour viewing period (depending on the title). Once you start watching these films, you'll have until the end of the viewing period to watch without using another play credit.
In-progress films appear on your Continue Watching list, which is accessible from the Continue Watching shelf on the Kanopy homepage and from the My Lists page.
For films with 48 or 72 hour viewing periods, you'll see the number of hours remaining until your play credit expires in the top-right corner of the film on your Continue Watching list.
If you hover over these films on your Continue Watching list, the title card will also display how many hours you have left until the play credit expires.