If you’re doing it outdoors and selecting the best plants — you’ll end up creating a line that’s perfect for your environment. By adding more and more genes, and selecting plants that best fit your area, you’re increasing the chances of the final batch of seeds containing all of the right traits needed to succeed.
You could definitely condense the timespan for a project like that, by running as many lines concurrently as possible. A few parallel projects that never interbreed until you’re satisfied both of them are full acclimated to your environment, and then making a true-F1 for that sweet sweet hybrid vigor