Retraction has a very big effect on print quality, especially in infill and thin areas, and also, the correct retraction can vary quite a bit between materials, meaning it needs to be calibrated for each material – including the expensive ones.
So, I designed this small object that requires a lot of retractions and doesn't waste a lot of filament.
This takes 13 minutes to fully print on my machine but it's usually pretty obvious if you have problem about half way into the print.
Print with no support, no infill and your usual printing settings.
Two little retraction will show as stringing.
Too much retraction will show as missing layers and really brittle legs, in really extreme cases of too much retraction the surface quality of the base will be horrible and the 4 legs wouldn't print at all.
Check out my other calibration piece at https://www.thingiverse.com/thing:1622868