Some newer caulks can bridge gaps up to a half-inch effectively. The depth of a crack or seam counts, too. Also, consider the temperature at the time caulk is applied. For example, if you apply caulk in the middle of summer, the substrate is fully expanded. If the caulk had been applied when the temperature was moderate and the substrate was between its fully contracted and expanded states however, the caulk wouldn't have to flex as far to keep up with the seasonal movement.
Some surfaces create more adhesion problems than others.
Oily or waxy wood and pressure-treated lumber are difficult to caulk. To get caulks to perform properly, clean surfaces of old caulk, dust, dirt, and any loose or flaking material such as splinters, of course. Sometimes you'll need to apply a primer to seal the substrate before caulking. So the higher up you go, the more important it is to use good caulks and apply them properly. Contractors working on high-rise buildings have to know the expansion coefficients of the building materials, as well as how temperature and humidity affect them and the sealants.