How can Paradise be an everlasting bliss with no sorrow or evil in it, while some believe that the existence of happiness necessitates the existence of sorrow, and that good necessitates the existence of evil in order to be felt and not become boring?

The rule "every pleasure has an end" does not apply to the people of Paradise, because they are in eternal bliss, where no harm or sorrow afflicts them, as confirmed by Allah's saying: "No harm will touch them, nor will they grieve." And His saying: "Abiding therein forever, they will not desire from it any change" indicates that they will not tire of the blessings nor become weary of them. Moreover, it is established in authentic hadiths that they will be healthy and never fall ill, youthful and never age, and blissful and never suffer, forever.