I've been hitting legs twice a week lately.  The second session of the week is much lighter and focused only on getting blood into the muscle.  Since I've come back to training after a long break I've noticed that I have trouble activating my outer quads.  When I was in my 20s, any leg movement would draw blood into my quads and leave my outer quads sore the next day.
Now that I'm in my mid-30s I've found that it's harder and harder to get blood into my outer quads, and it's getting rarer and rarer that my outer quads are sore after training.

So, in an effort to avoid the mid 40s turnip leg syndrome that I've seen on so many older bodybuilders, I'm using a second leg day each week to focus on my quad sweep

 

Quads:
Bulgarian split squats:
3x15 bodyweight
Drop set:
1x15 60lb
1x15 30lb
1x15 bodyweight
10 second hold at the end

Reverse hack squats (squats while facing the hack squat machine)
1x20 135lb
1x15 225lb
1x15 315lb
1x15 405lb

Sissy squats (on sissy squat machine/apparatus)
3x15 bodyweight

Walking lunges
1x50 each leg (brutal)