For me I do the 50 reps, I simply break it down to 10 sets of 5 reps. I can grind out 8 reps for a few sets but since I do it as a superset in between benching that seems to defeat the purpose. With sets of 5 I can do good, crisp, explosive reps and still have enough to give my all to my bench reps.
I think I saw recently on his blog or a recent T-Nation article that Jim was pushing 50 reps of chins, 100 reps of dips and 100 reps of back raises. I can do all of those by breaking them down into 10 sets. This works out pretty well when I superset the sets with the main exercise: 3 warmup sets, 3 work sets, 5 sets of FSL.