My examples:
60 single for high coverage WB, 60/90/60 on whites, or anywhere you need to put down more ink. 80 duros for fine detail, or just to put down a thinner layer, we use 80's to cut back a color that is too strong or to reduce dot gain in a sim process print, or to keep colors on a base from smearing during a run.
70's for day to day spot color stuff.
UB's we use 70 a lot, 60/90/60 a lot, depends on the result we're getting, sometimes a duro change is just what the Doc ordered.
It all depends, I used to have all 70's too, but I wouldn't be without a variety of squeegees now.