FWIW, I trained Deads 3x week (M, W, F), 2 sets of 10's and 3 sets of 5's until I was nearing my 5RM, then I only did 2 sets of 5. Also, nothing else in my life taxes my lower back. I sit in a chair most of the day, typing on a keyboard, so my time between workouts was pure rest for my low back. I'm sure that makes a pretty big difference, and is a key reason I can train deads 3x week.
Also, I think my cardio sessions between workouts (T, T) did a lot of good for my lower back. Rowing, especailly, the rowing sprints I've been doing went a LONG way to speeding my recovery by bringing a lot of blood and nutrients to those tired muscles.