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Actually, there is no such thing as an agreed-upon 100% perfectly complete SEO project.  Some might call that just doing what's necessary to bring a site up to a basic threshold, some  might say there are always more keywords to go after, more backlinks to get or more social signals to go after. Still, others might say that if you're not ranking in Timbuktu, then obviously you're work's not perfect. On the other hand, most might agree that the results of one tool, in particular, would be the best indicator of a perfectly executed SEO project. That would be #1 results ong google across the board for all of your target keywords--and what the heck, having #1 results for all of your competitors' target keywords, as well. Anyway, look at google adwords keyword planner and see what the approximate traffic for the #1 position of your keywords and that will give you a hint of what you could be getting.