It's not about rushing to metaphor, is that it always did mean metaphor.
The 6 days
Before going into this we have to see some of metaphors in Quran, to get familiar context.
Earth as darkness and selfishness and lust
And if their turning away is hard on you, then if you can seek an opening (to go down) into the earth or a ladder (to ascend up) to heaven so that you should bring them a sign and if Allah had pleased He would certainly have gathered them all on guidance, therefore be not of the ignorant. (6:35)
My comment: Obviously there is a link to bringing the ultimate sign of his Nubuwa and Authority (Mohammad), with the meaning of opening into the earth or a ladder to heaven/sky, so we see heaven/sky and earth can have metaphorically understanding. This can't be literal, so there is a meaning. Going down suggests earth represents darkness and low nature of a human. This while heaven/sky represents the light reality the heart is linked to.
Had We wished, We would have surely raised him by their means, but he clung to the earth and followed his [base] desires. So his parable is that of a dog: if you make for it, it lolls out its tongue, and if you let it alone, it lolls out its tongue. Such is the parable of the people who deny Our signs. So recount these narratives, so that they may reflect. (7:176)
My comment: following his desires is obviously synonymous here with clinging to the earth showing earth has a metaphoric meaning with lower nature of the human spiritual kingdom.
Heaven/Sky where lights are found
13And even if We open to them a gateway of heaven, so that they ascend into it all the while, 14They would certainly say: Only our eyes have been covered over, rather we are an enchanted people. 15And certainly We have made strongholds in the heaven and We have made it fair seeming to the beholders. 16And We guard it against every accursed Shaitan, 17But he who steals a hearing, so there follows him a visible flame.
My comment: A long with the first verse I quoted, we see not only is heaven a place where the lights of guidance are found, but ultimately, the heaven/sky reality is guarded from every devil. The visible flame that follows intruders suggests the stars of guidance are living beings guarding this realm.
7 Earths 7 Heavens mirror each other
It is Allah who has created seven heavens, and of the earth [a number] similar to them. The command descends through them, that you may know that Allah has power over all things, and that Allah comprehends all things in knowledge. (End of Surah Talaq)
My comment: We see heaven and earth mirror each other in this respect. This a major illusion, it's about light and darkness aspects of a human.
The morning and 10 nights and pair and single
In Surah Fajr the night has been according to some hadiths, seen as a metaphor of Imams (a) being veiled and their reality and proof become less vivid and clear.
It can be seen as a warning, because the verses after, are talking about how God dealt with oppressive nations. It can be seen in that light, if the lights have become veiled due to oppression towards truth, then God's wrath may take place like past destroyed nations.
The fajr (morning) is said to be Imam Mahdi (a) according to the hadith. The 10 nights Hassan (the 2nd Imam) to Hassan (the 11th). The pair being Ali (a) and Fatima (s). And the single/alone being Mohammad (s).
It can be seen this is if things go wrong. Now I am saying this because Quran has analogies and metaphors of night so that we can discuss in light of this what "6 days" means.
The 6 days as metaphors of leaving darkness towards light.
It can be seen every time we leave one veil of darkness, light is unveiled, but no darkness is without light. And so after the 6th tearing, the final veil is when "God establishes himself on the throne (of the heart)".
This can be seen that 7 earths are stages, 7th earth is when we finally enter to the sky reality and light, which then has 7 veils of light.
The Quran in this way is describing the journey of the first human Adam (a) when describing the creation of earth and heavens.