Rest/Recovery is why you workout. Longer recovery is absolutely necessary in many situations and if more than normal soreness is the result of a workout. Working out sore muscle groups wastes the previous workout and may result in injury. And for most highly trained exercisers, 5 to 10 days of rest in a row are often very beneficial once or twice a year.
There is much more to recovery than the average fitness instructor understands. I teach a series of CECs on recovery. Many of the students that have taken the class report to me that they experience previously unattained results once they properly apply recovery in their programs.
Anyone interested can check out my website, www.hawaiifitnessacademy.com .