I am doing almost exactly the same thing, loving the convenience of the zoom, and leave the 50mm F1.8 in the dry cab.
When I first bought it, I played with it quite a bit and compared it with my zooms. At 8R or smaller, there is so little difference, so, it gets to see the sun less and less often, so much so that it hs been in the cabinet for a year.
So, recently, I sold it off, to make some space in the dry cab to get something else.
still new to the game, but I used two primes (35mm f/2 and 100mm f/2.8 macro usm) once a while. had thought of getting the 85mm f1.8 but was also eyeing the 70-200 f4L
Got more prime than zoom but depending on the occasions to use.
The 180mm Macro for Macro mainly.
50mm f1.8, 90mm f2.8 macro and 135mm f2 L for portraits and low light shoots.
Don't have a super long telephoto or super wide prime, so relied on zoom lens for distance animal shoots and wide landscape shoots..