Daily!!
I have a tucker mono with pencil and fan jets, I have a 14" stiff bristle with 4-6 jets, gardiner super lite, a compact with three jets(my fave), an extreme, a supreme, one of them gardiner yellow ones too which I like. I just sold an xline rinse bar brush which was for me crap.
I run 2 jets , 3 jets , 4 jets, 6 jets, 100 degree fans, 50 degree fans and I have just bought a flocked compact which I will be putting a rinse bar on when it arrives!!
Proper brush fetish! They all have there uses, the tucker has strong bristles and is great for first cleans, the extreme is so light its great for hard to reach and high windows. The 14" for large panes.
These will last ages being swapped around, usually you can tell when a brush is goosed just by looking at the bristles.
On the gardiner website it gives a guide as to how long each brush will roughly last.