5 stars heros

Why is it that we don’t have the option of selling of the 5*, when we can not use them because we have no heroes duped, and in The end we just lose them after The allowed period?? This happens when we purchase them or earn them. Since we don’t have the option of selecting our own heroes when we have all the crystals.
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Comments
Moreover what do you mean by "lose them after the allowed period"?. There's no way you can lose a champ if you own it unless you sell them and in the case of 5*, even that's not possible.