Joe, all good points.
Have you looked into incorporating Myo Reps so you do less total reps but equal or greater effective reps allowing you time and energy to work other secondary muscles such as the arms?
I use them at times...for example if I can't get to the gym I may do a set of bodyweight squats really slow and almost to failure were it starts to burn around rep 25 to 30...and then rest for about 3 seconds and keep going up until about 50 reps and stop.
I Also do this with pushups when I can't get to the gym. Bodyweight movements like I just describe basically prime my body for the next day when I can get back into the gym.
Other times when I don't feel like messing with myo reps I will just take a weight around my 20 rep max and do 3 sets of 15 reps and call it a day.
Basically my workout looks like this every week.
Monday (pump day) 50 reps with my 20 rep max. So it may be 3 sets of 17 reps.
Tuesday 4 sets of 6 reps with my 8 rep max.
Wednesday 4 sets of 10 reps with my 12 rep max.
Thursday is off.
*** interesting notes*** I have started doing pec dec flys on my Wednesday work for 2 sets of 10 reps. And I can't explain it and its technically a pre-exhaust old bodybuilding trick (that I know some experts save pre-exhaust works other don't) but anyway for some ODD reason the stretching and 2 set workout from my pec dec flys actually causes my dip workout to be able to lift heavier weight??? I don't know why...but my guess is the flys are stretching out my shoulders and they feel 100% better when doing dips?
Again I know this goes against the grain and everything we have been taught....you would think flys before dips would make my dips weaker but it doesn't and I love doing them this way.
The only issue I am running into right now like you said above were to fit in shoulders and arms.
I just kind of throw shoulders and arms into the mix whenever I feel like it no set schedule...this could become a problem down the road...its to early to tell.
My thinking and HOPE was with all the pushing and pulling 6 days a week my shoulders would get enough training without having to actually work them with a direct exercise...the same with arms.
I don't know if this will hold true or not? But my arms have grown the past 3 months and I have worked them less than normal?
I have been reading a lot of work by Dan John as well as Pavel and others and there are a lot of opinions (not much research) that seems to think as we get older and closer to 40 years old frequency should increase and stay away from failure.
If you look at the Norwegian frequency project you will see that those guys worked at around 70% of there maxes staying well away from failure and they train 6 days a week. They also use a higher volume than I do.
Borge Fagerli has a great article on this and I looked at his dose response curve of how many sets per muscle group to be optimal. Bascially 4 sets is about the sweet spot of training for the average lifter. So using that logic I set my routine up for 4 sets and just varied the reps from low to high...which equals between 24 to 50 reps depending upon the load.
But back to your point what I can't figure out is if I should fit shoulders and arms into the routine everyday or just as needed. I guess one could always cut sets by 1 across the board and then add them that way. So instead of 4 sets of push pull legs...you could do 3 sets of push pull legs and then that would give you room for 1 set of shoulders / bicep and tricep.
I just have really gotten use to not training arms...and to be honest I don't even like direct arm work anymore because I like training minimalist full body...I am more into functional training now and not being all show and No go...if you know what I mean.
But the old bodybuilder in my from 20 years of lifting still wants to do some curls every now and again!