Which airport are you flying out of? I think by 5pm traffic will start to wind down. It definintely wont be the "madhouse" of Wed evening. Also, will you have any type of status for premier checkin?
I fly out of SFO a lot and even on the busiest days, the security line moves very quickly. I've never been in line for more than 15 minutes.
OTOH if you fly out of IAD, we've heard postings of hour long waits.