Hey, preface all of this with the fact that what follows are my thoughts, words, and ideas. There are a number of companies that supply "canned" content that the individual can use to publish,post, or blog as original content. Good bad or otherwise, what follows is all original to me.
With stucco, the question is not IF it will crack, it’s a question of WHEN it will crack. If there is a crack, water will want to penetrate through that opening. Nature may be lazy (following the path of least resistance, etc), but it never misses an opportunity. Know that I am not speaking about wide cracks ¼” or greater in width, but more to hairline cracks. These cracks, due to the pressure differential between the outside of the home to the inside will draw moisture into the homes wall cavity.
Points of stress in a building will tend to be concentrated at the big openings. Window and door openings will invariably have hair-line cracks form at their corners. These cracks will tend to radiate up (from the top corners) or down (from the bottom corners) at an angle. Secondary to this, stucco will show vertical cracks in expansive open areas of a wall. Historically, inadequate or errant installation of flashing around window and door openings has been the vulnerable entry point for water in stucco homes.
For the homeowner, regular monitoring of these hairline cracks is important. More than just noting that there are cracks on the exterior, the homeowner should keep an eye on the interior side of that crack. Specifically, water, once inside the wall cavity, will tend to follow the wall framing to the sill plate (floor level) and come to rest at that point. The home owner should look for staining, soft spots, and noticeable water intrusion.
99% of everyone will take care of a serious home issue once they are aware of it. If a basement or attic space has a noticeable blob of mold or a wall section is showing deterioration and rot they will be moved to action and correct the issue. The challenging part about water intrusion trough wall claddings, stucco included, is that moisture sets up shop between (in the wall cavity) the exterior and interior walls, unseen by the home owner. In these cases mold can grow unnoticed and wood components can rot.
Regardless of the exterior material that protects your home, regular assessment of your exterior finishes, their integrity, and the correction of any defects should become a regular part of any homeowners periodic maintenance.