IF QC departments were perfect there would be no need for recalls. Who decides how long to test a product before releasing it for sale?

A one-day test? One week, one month one year? Defects sometimes don't show up for years.  Quality Control.  Quality Assurance. Safety tests. Is there a specific science behind it or is it just scattershot hoping for the best?  Cars are being recalled all the time. Is that normal?