You don't actually have to stick to any rep range at all, the 15/10/5 set up is to make the cycle easier to set up. I do a different number of reps each session as I go to 1-2 reps short of failure - so my '10s' equivalent might be 15,12,10 and my '5s' eqivalent might be 8,6,5. I usually do a...