Battery Life and Cases for the Smartphone

[AC Question]

The users manual for the Samsung Galaxy S6 Edge advises the user not to cover the lower end of the phone because that is where the antenna is. If you cover it, the battery will run down quickly. If this is true, does this mean you shouldn't use a cover for the phone while it is in use? The manual recommends only Samsung approved screen covers. I'm concerned about this because the phone is over $800 and I feel a need to protect it somehow.