I've recently noticed that this is not possible to start over a course challenge, which I wouldn't say I do care much about, but it's still a bit annoying when you entered an answer wrong not because you solved it wrong but because you made a typo entering the answer. 

My question is, if you leave a course test unfinished for a day, or a week, or a month, will it eventually reset because it has timed out, or it will display "Resume course test" link forever?