Depends on a lot:
How old are they?
How big is your cage?
Will they have duplicate basking spots? Hide areas? Lots of cover? Multiple food bins?
Who told you this...a successful long term breeder or a commercial dealer?
Keeping them together will stress one or both of them. The less dominant cham will eventually get stressed to the point of being sick. The male will constantly try to breed even if the female is not receptive. They could actually injure each other. In the wild they would not normally share a space as small as the typical cage. It is much safer and more humane to keep them separated.