I have never heard of crowds in January, even on the holidays. I've been many times in February and the park is a ghost town in the morning.
Now, if you want to sleep in, and visit the parks in the afternoon, then having FOTL may be worth it. The park comes to life in the afternoon, with waits of 30-45 minutes for the major attractions. The parks close early, at 6-7pm, so remember that.
If you wake up early, and arrive the gate before they open at 9am, then I'd say no, you don't need FOTL.