Heaven is eternal and Earth everlasting. They can be eternal and everlasting because they do not exist for themselves, And for this reason can exist forever.
As to those other things which we hold on the authority, not of Scripture, but of tradition, and which are observed throughout the whole world, it may be understood that they are held as approved and instituted either by the apostles themselves, or by plenary Councils, whose authority in the Church is most useful, e.g. the annual commemoration, by special solemnities, of the Lord's passion, resurrection, and ascension, and of the descent of the Holy Spirit from heaven, and whatever else is in like manner observed by the whole Church wherever it has been established.
Heaven and Earth last for ever. Why do Heaven and Earth last for ever? They are unborn, so ever living. The sage stays behind, thus he is ahead. He is detached, thus at one with all. Through selfless action, he attains fulfillment.
It is our duty not to not only hold fast, but to hold forth the Word of life; not only to hold fast for our own benefit, but to hold it forth for the benefit of others, to hold it forth as the candlestick holds forth the candle, which makes it appear to advantage all around, or as the luminaries of the heavens, which shed their influences far and wide.
A buddha is someone who finds freedom in good fortune and bad. Such is his power that karma can't hold him. No matter what kind of karma, a buddha transforms it. Heaven and hell are nothing to him. But the awareness of a mortal is dim compared to that of a buddha, who penetrates everything, inside and out.