Avi,
Depending upon your level of conditioning and expierence 20 reps is most likely plenty, considering you are using adequate weight.
Max stim guys make great results with 20 reps.
Some of us you more reps...me personally I try to keep mine in the range of 24 to 36 reps. meaning I go as low as 4 sets of 6 reps (heavy weight) and I go as high as 3 sets of 12 reps.
The majority of the guys on here shoot for 30 reps ...and that is most likely what I probabley average myself.
However there are times when I think a planned overtraining or overeaching program has its benefits.
These time could be at the very end of a program before SD.
It could be used to bust through plateau...etc.
Volume is a unique thing that within reason can shock your body.
What I mean by this is normally speaking take the opposite of what you normally do and do it.
So for example I am in the middle and 3 weeks away from ending my overeaching cycle of chest and back specialization. I am using 40 to 50 reps of with 70% of my 1 rep max Load.
Now this overeaching has gave me a great look and pump...but I have about milked it for all that is worth now 3 week into it.
What I will do next is a long SD about 2 to 3 weeks and then start back with 20 reps.
If SD works like its suppose too (Im not so sure that it does???) this will work fine....but even if it doesn't it will give me a break and allow me to get back use to some heavier rep ranges.
Im not sure if I helped you any with my answer but WAVE LOADING and playing with volume has been around for decades and its a lot of fun to CUT UP using it instead of cardio!
Long story short if done properly WAVE LOADING can be beneficial IMO.
However when its all said and done I was come back home to HST...but 13 years now into the IRON game I need something 2 or 3 times a year to break up the boredom!