You could spend 30 mins inspecting a modestly complex board manually using a magnifier/scope and still miss things. Humans get distracted, bored and tired. It is also difficult or impossible to visually inspect some faults like mild tombstones or quantify/verify a solder joint fillet as being within spec. All modern AOI machines claim very rapid programming times and these become more attainable the more comprehensive your libraries become and the more product you put through them.
If you have AOI I think you should maximize its usage. Ideally it should be true AOI but any assisted inspection aid is good.
Equally it is important to learn from what you find in AOI, keep and analyse those results and feed that back through your SMT process. Hopefully you will get fewer faults at AOI and later testing.
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