I train legs once a week. I go hard and heavy every time. Can hardly walk afterward. I couldn't even think of doing legs again for at least 4 days or so. Often, I am still not at 100% at day 5.
Sometimes I wonder if I'm just overtraining, but my max is moving up, my body weight is moving up, and aside from the day after legs I feel energized and healthy.
I have been thinking about doing less work on leg day and doing it twice a week.....maybe.....some day.....but I love crushing them in one workout.
FYI, my current leg day is squats, leg press or hack squat, leg extension, a couple exercises for hams and a couple for calves. I vary the ham and calve stuff. 45 minute workout. I focus on intensity for every rep instead of loads of sets and reps. I go to failure almost every workout.