One other little thing to remember is that 15s are beneficial in another way: inducing hypoxic/oxidative stress creates an environment that promotes joint and tendon health. So you need to get a burn going during the 15s to prep your joints etc. for the heavier stuff to come. Because I don't like doing slow reps, I tend to do more reps when the loads are at their lightest. I might get to within a couple of reps of failure in order to get a really good burn; that might take 25 reps with the lightest loads!
"Be the best that you can be."
Deadlift: 215kg (474lb) - pre-hernia!
Low-bar Back Squat: 190kg (419lb) 16/04/10 @BW ~210lb
Bench: 130kg (287lb) 01/02/13