Also depends on which side you are entering from. I have seen long lines for bag check in the evenings at Mickey and Friends, but I have never seen long lines in the evening at the Harbor side, though I'm sure it happens. There is no one answer.
We usually arrive in the evenings on Saturdays and go through bag check at either M&F or DTD. Rarely have we waited for longer than 5 minutes or so in line, usually less than that. Bag check at the GCH/DTD entrance can take a bit longer, but usually no more than 10 minutes at the most.