The Knazone took about two months, Bluzone took about six months, Bluzone 2 took about a year and a half...
So far this has taken me about half a year a-hoo-hoo!
I'm thinking of making it a 6 hour cycle, to be honest.
48 minutes is just way too short-- sometimes you'd spend that much time having a conversation.
I've done some in-game testing, and placing it on that cycle while I build and it feels comfortable.
And don't worry-- night won't be pitch black. I'm aiming for it to be very stylised in how I approach many things. Very dramatic, larger than life. This isn't veering so much toward realism as some of the others were-- but that's not to say it's won't be just as punishing.