When properly brewed for their second and third, even fourth, round (depending on the type of leaf)you will find that the flavor profile changes and new nuances come out... it's NOT just a weaker version of the same flavor.
Multiple brewings of the premium whole leaf teas is very traditional.
It's the way I have always done it...
And the way recommended to me by my friend who's close friends go to select premium tea from farms themselves (owners of Teance in SF)
I don't think that you are hurting anything by doing that... and as long as you are extracting flavor, you are certainly extracting some good chemical compounds IMO.