Houston humidity, Valley heat, and relentless UV are hard on an exterior coating, but they are not what makes most paint jobs fail early. What fails is adhesion, and adhesion is decided before the first gallon is opened.
The sequence that works is not complicated. Wash the surface and let it dry properly. Scrape and sand everything that is loose or chalking. Treat and prime any bare wood the same day it is exposed. Re-caulk the joints with a product rated for the movement they actually see. Prime the repairs and any bare or stained substrate. Only then apply the topcoats, and only in conditions the manufacturer allows.
Skipping the wash is the most common shortcut, and it is the most damaging. A chalky south elevation has a fine powder of degraded binder on it. Paint applied over that is bonded to the powder, not to the substrate, and it will sheet off in a couple of seasons no matter how good the paint was.
Caulking is the second. Joints between trim and siding, around windows, and at corner boards move seasonally. Painter's caulk that was never rated for that movement splits within a year and gives water a direct path behind the coating, where it causes rot you will not see until the trim is soft.
The third is applying in the wrong conditions. Gulf Coast afternoons routinely sit outside the temperature and humidity range printed on the can, and applying anyway means the film never cures properly. That is a scheduling problem, not a paint problem, and it is fixable by planning the day around the weather instead of the crew's convenience.
When you get an exterior painting estimate, the useful question is not which brand of paint. It is what prep is included and how it is written down. If the answer is vague, the price is not comparable to anyone else's.