I've had 4 weeks (5th-8th week hit PRs) of progression, twice. I've had 6 weeks of no progression - 6th week was supposed to be PR week, and did not get my reps. I think I reset back.. I forget. I really ran this, or a variation of it, many times. :-/ When you stall, I say switch programs. If you run it again, I would change the lifts, or rep scheme.
Anyway, I think 4 weeks of PRs is pretty good. If you gain more body weight, you'll go further.
I only ever used the spreadsheet for the advanced version, and that went well (I did lower my maxes by 5 for bench, and 10 for squat & bench, however).