In applications? Sometimes. The kernel is a different matter. Speaking generally, the BSDs endeavor to not commit "revisit this later" code to the kernel at al

In applications? Sometimes. The kernel is a different matter. Speaking generally, the BSDs endeavor to not commit "revisit this later" code to the kernel at all. In the idealized development approach of the BSDs, it's either done right, fully analyzed for performance impacts across the usage spectrum, long-term API maintainability, security, et al, or it's not done.