I've been reviewing my program and I've been doing far too many sets of delts in a week.

The main reason for this is most chest exercises use front delts as a primary or secondary muscle, and most lat exercises use rear delts. I count a secondary muscle as 1/2 a set, e.g.

>4 sets of bench press = 4 sets of chest, 4 sets of front delt
>4 sets of decline bench = 4 sets of chest, 2 sets of front delt

Even with my new program I get
>14 sets of front delts
>8 sets of lateral delts
>12 sets of rear delts
which is 34 sets of delts per week?

This is still way above the 10-20 sets per week. Can't I just do 10-20 sets/week for each head? Different sources I've found disagree on this.

The only way to get under 20 sets / week total would be 6 sets per head which seems way too low