Once upon I time I was a scene painter in the theatre and as such I had special paint brushes which I still own and use.
Some of them are over 35 years old.
One of the most useful brushes of which I have 3 (or maybe 4) is a “lining” brush. In scene painting a lining brush is used at the end of a bamboo pole with a lining stick to make outlines and shadows. In its use at home it’s great for window frames and interior trim.
I also have a few newer brushes (none newer than 5 years) which I use to paint trim, stripe in the boundaries of a wall (before rolling it) and furniture.
When I dip a brush in paint I’m careful to keep the ferrule out of the paint although it sometimes gets up into it when painting upside down or overhead. I try to keep my brushes impeccably clean by rinsing them with cool water and brushing them with a wire brush after usage.
I seldom use soap or detergent to clean the brushes. I do however have brush cleaner in which I soak my good brushes to loosen up any old debris. I rarely do this as the water and wire brush method seems to keep the brushes supple.
When necessary, however, I pour brush cleaner into a metal can up to the metal ferrule and hang the brushes in the liquid for a few hours or overnight.
Then I use the wire brush/water method, sometimes adding a bit of liquid detergent, to remove the oiliness.
Now my brushes are ready to get back to work.
Do you keep old things hoping to rehabilitate them one day? (I think I already know the answer to the question. HA!)