I’m curious about approaches to test retakes and flexible deadlines.

When it comes to retakes, do you allow them? What's your reasoning for that policy, and under what specific circumstances do you allow students to retake an assessment? I'm also curious about the logistics - for example, do students have to complete a review assignment first? 

Similarly, how do you handle deadlines? Do you set hard deadlines or build in flexibility? I'd love to hear the philosophy behind your approach. For those who are flexible, what does that look like in practice? Do you use a grace period, for example?