Depends on the length of the drive and where I'm going. I have done overnights in the past, from WI to TX or WI to FL, with other drivers along, taking turns. Also from here to WI with DH. Shorter drives, like the ~14 hours to Vancouver, we do in one day, leaving early in the morning and arriving around dinner time. I don't think I'd want to do that one at night.
Other times we'll set out once DH is home from work, stop a few hours away (Lloyd, Saskatoon?) and then finish the rest of the drive the next day. He is too tired after work to drive much further, so most long trips are started in the morning.
I'm doing the 24 hour drive (not including stops) with J to WI next month, and he isn't an awesome traveler. While I'd LOVE to be able to drive at night, so he would sleep, obviously that wont work this time. Instead, I'll start very early in the AM and hope to get a couple solid hours in, then stop often and quit traveling early in the evening. The plan is 2 days, but I've allotted a possible 3 each way.
Also - when I go, I pick out something comfortable and put him in it the night ahead of time, and I also tend to recline his car seat back a hair the night before. He sleeps better that way.