Changing the bedding...
In about six weeks, you may begin to see noticeable changes in the bedding. Although you add food waste regularly, the bedding volume will slowly decrease.
As more of the bedding and garbage is converted to castings, extensive decomposition and composting by other organisms in the bin also take place. As time goes on, the proportion of castings increases as the environmental quality for the worms decreases.
There will come a time when so much of the bedding in the bin becomes castings that the worms will suffer.
Because each system is different - depending upon bedding used, quantity of worms, types of garbage fed to them, bin temperature and moisture conditions - it is not possible to predict precisely when you must deal with changing the environment of your worms. It is important to get them away from their castings and preparing fresh bedding for them at the right time.