Software and Popcorn
When releasing software, you spend a period of time shaking it up hard trying to find and fix the bugs. There is a point during this time that you know some bugs still exist, but to wait any longer will cause the whole release to be out of date and less useful.
When cooking popcorn you spend a period of time heating up the kernels and shaking them about trying to make them pop. There is a point during this time that you know some kernels still are unpopped, but to wait any longer will cause the rest of the popcorn to become burned and the whole batch to be less than tasty.
Figuring out the right time to take the popcorn off the heat is very much like figuring out the right time to release software, known bugs and all.