Can't speak to the wait times at SDD this January, but our experience has been that getting to the gates 45min-hour ahead vs. right at opening actually saves MORE than 45min-hour of waiting time in line.
For example, if you arrive right at opening for FOP, your wait time will be 2hours+ in line, vs. walk on if you had gotten there an hour ahead. So, you would cut your wait time in half right there. 7DMT jumps to about 75 minutes+ right at park opening.
So, by getting there an hour earlier you are often saving a 2+ hour wait in line, not 1 hour. Yes, you could also have a shorter wait at the end of the night. It's really up to you whether you want an early morning or a late night. Totally depends on personal preference