I have 5 #187 brushes... I wash them every 6 weeks. I know they shed, that's why I use each brush for a different color.
Ex.
1 brush for cotton pink color blushes (NARS angelika, MAC sweetness etc.)
1 brush for peach color blushes (NARS gina, MJ peach)
1 brush for foundation use (I barely use the #187 for foundation, because then I gotta wash it often, and that causes shedding~)
1 brush for rosey pink blushes (NARS deepthroat, orgasm, oasis, MAC pinch o peach etc.)
1 brush for darker color blushes (NARS lovejoy, MAC prism etc.)
this way, I don't have to use the shampoo (sephora) to clean them often. right after my every use, I just wet the beauty cotton w/ MAC brush cleanser. And wipe #187 brushes gently on the cotton~
*I keep my brushes in a clean container w/ a lid. that way no dust! and I use anti-bacteria spray inside of the container every week, gotta keep the container clean!