Precompiled code is useful during the development cycle to reduce compilation time, especially if:
You always use a large body of code that changes infrequently.
Your program comprises multiple modules, all of which use a standard set of include files and the same compilation options. In this case, all include files can be precompiled into one precompiled header.
The first compilation — the one that creates the precompiled header file — takes a bit longer than subsequent compilations. Subsequent compilations can proceed more quickly by including the precompiled code.