|BEST PRACTICE: Patches and Non-Major Updates can be dangerous!|
In general after building a new MSI package I give it a good test the first time (concentrating on areas I may not have used before). After this initial testing unless my MSI source code needs changing for newer versions (see "Don't change the .MM Script!"), I only quickly test my MSI if at all. If I have made changes then I need to test more but still concentrating on the changed areas. I can do this as I've been careful when writing my script and I trust MAKEMSI to detect and report any build time issues
Using major updates means that in general every build you do is exactly like another and may need no Windows Installer skills at all (depending on the changes).
|The Alternative - Every Build is Different|
In general I'm not in favor of patching or the many variations of upgrade types because they greatly increase the build complexity and the amount of testing you need to do. Because of this much greater Windows Installer skills are also required.
Most of the problems you'll see in any MSI related forums will be about issues with patches and involve updates other than major.
One of the reasons for the complexity is having to be much much more aware of the specifics of the previous installs than you should need to be and the fact that the build of every MSI becomes different.