The purpose of a layoff is to refresh the body as well as the mind from the rigors of heavy training, as well as to recover from soreness and injuries. The frequency of layoffs, their duration and what should be done during one, vary from lifter to lifter, but all should consider the same major factors. Each athlete possesses his own unique ability to recover from exertion. This can be aided by nutrition, lifestyle and sensible training, or negatively affected by poor nutrition, bad training techniques and wild lifestyle. Of course age and general health are critical factors.
Scheduled layoffs are the best way to go.
For example, after a competitive cycle, a lifter should take some time off, a few days to a few weeks. If major soreness or an injury exists, then layoff should be longer. However, if the pain or injury does not affect training on other lifts, then you could resume training on the unaffected lifts sooner. Training intensely when you are experiencing chronic pain is asking for trouble. This type of pain requires an immediate, unscheduled layoff.