When it comes to working with a team, most of the time 80% accurate is good enough.
As you know, time is money and most of the time large projects have time-‐
constraints. If you are working with a team, achieving 80% accuracy is almost always good enough. You can leave the remaining 20% for the practicing or testing phase, where you can work out the finer details. Keep in mind that getting the job done right and on time is more important that getting al the details right.