Davina, having multiple wigs when full-time is pretty much a necessity, as the darn things can take 16-24 hours to fully dry. I have two in my daily wear style, as well as one in the same color, straighter and slightly longer, as 'dress hair' when I need to look a bit more posh, as you might say.
Washes take a bit of life out of the wig, so minimize soak time in the wash solution, and get a good spray-in conditioner to use on the damp wig after washing. Don't try brushing till it is completely dry.
When brushing avoid the temptation to start in with big strokes. Spray conditioner on the ends, and brush out the last inch or so all around. Then, go back and brush out the first couple of inches. Then, do the first 3-4 inches. The idea is to avoid long sweeps that compact pre-existing tangles at the ends, leading to crimping of end hair, breakage, and a premature death from the frizzies.
All lessons I had to learn the hard/expensive way.
You may even want to consider using cheaper synthetic wigs for daily wear, in a style you like of course, and get better wigs set in a similar style and color for evening and weekend wear that won't need to be washed nearly as often.
Best of luck at the GP's office, and I hope you get some answers there.