This is a great topic to bring up. Many people, as you had mentioned, view missing milestones as a terrible thing that can occur in a project. Which is undoubtedly true. However, in my opinion, missing deadlines is significantly less detrimental than rushing to meet that deadline. I’ve personally witnessed many situations where we need to go back and retest certain parameters of products that were rushed during the projects. In addition, many unexpected situations can arise from a project that was rushed and not well thought out before freezing designs and releasing the product. Obviously it would be ideal to set appropriate deadlines that are realistic to be met for a project to be successful, but if it comes down to it, facing the problem during the project immediately and dealing with it appropriately is better than allowing it to manifest and grow into something worse later down the road.