I think there's something special about a song that is written quickly. There's a big difference between something being rushed and something just naturally coming together. Sometimes you come up with something that just works. The opposite extreme is that you spend a long time on a song and the original purpose gets lost and the result is underwhelming. Look at Chinese Democracy for example. Some decent stuff on there but it sounds like Axl was overthinking it.Some people make it sound like this album (which they haven't heard) consists of the first ideas that came to the band's minds. They were in Paris for at least a month. That doesn't seem like a quick bang-it-out to me.
How long did it take to record their early albums?
Also, I'm not sure more time equals better album, or even more polished.
Rush worked on Vapour Trails forever and it turned out sounding like mud.
Def Leppard lost any vestige of metal credibility polishing Hysteria to a sheen.
These guys have been writing songs for a long time. I wouldn't be surprised if they do it in their sleep at this point. Finishing the album relatively quickly isn't something to be alarmed about. Quite the opposite in fact.