Family of 3 (2 adults, one 16-month-old), and let's say 3-4 loads of laundry a week on average.
We separate out whites, darks, and delicates (because it DOES make my work shirts last longer and look less worn if they're not being bashed about with jeans...). At least a load of darks every week, whites every two weeks, delicates every week and a half or so (aka: when I run out of work dresses and shirts...)
4th load is sheets/random house linens. We wash our bed sheets every 2 weeks (when they start accumulating cat hair), but my daughter sweats in her sleep and soaks her sheets through nightly, so those need changing much more frequently or they smell like stale sweat (charming baby, I know).
Could we do less? probably. Would the time spent managing what the rest of the household is doing with their clothing and linens be worth it to me? Not even remotely. Pick your battles, y'know?