Impossible to say on how long to hold a particular base/run. Changes by the week. That said, from what I remember, LUK opened up less often than some others. I tried to move to Nashville for about 3 months, and nothing opened up. Then it opened up the week after I had committed to stay in St. Louis for upgrade. The good news is if you do your month or two somewhere you don't want to be, they'll work hard to get you where you do want to be, but no guarantees.
There weren't a whole lot of night runs at CPS, and the ones that there were were short and back before midnight. However, Florida is full of all-nighters, and I know at least some of the BNA Baron runs flew during the wee hours.
You'd be amazed at how used to not seeing your girlfriend much during the week you can get
. Also: How did your poor fragile snowflake handle it when you went out on a four day? Even if you get a day run, if you want to make any money, you're going to have a long duty day, often 12-14 hours. When you get home you're not going to be in any shape to play house. That's why it's called "work", son.
Incidentally, if you want to do a little scouting on runs, open flight aware. The flights all have three digits. First digit "3" indicates Nashville (and Atlanta, maybe?), "7" St. Louis/Little Rock/KC, "9" Cinci, "1" Orlando...Can't remember em all, but you get the idea. Or, if you prefer, just click on the airport and scroll through the arrivals/departures for the "FLX" prefix.