If a man consistently fails on his third attempt in the deadlift, he should get his max on the second attempt. On a good day the opener will feel light. On a bad day it will feel heavy. These figures are mine arrived at after 30 meets and averaging the successful lifts. But the figures won't be much different for other lifters.
Most people can do well training the bench and squat twice a week and the deadlift once a week.
I found once every 8 days for the squat worked better for me.