Everlastingness
Everlastingness is necessary for Allah, meaning that non-existence does not follow His Existence, because once it was confirmed mentally that Allah is Eternal, it was necessary that He would be Everlasting. This is because had it been possible that His Existence would be followed by non-existence, Eternity would not be applicable to Him. Therefore He is the One Who is Everlasting by Himself, there is none Everlasting by himself except for Him. As for Paradise and Hell, their everlastingness is not intrinsic, rather it is because Allah Willed for them to be everlasting. Hence, it is valid that Paradise, in and of itself, would go out of existence. Likewise Hell; in reference to itself it is valid that it would go out of existence.