I keep 10% ferricyanide and 3.5% potassium bromide solutions on hand and mix equal amounts of them with differing amounts of water to make working solutions of a rehalogenating bleach. The stronger, the faster acting. It's easy to start weak and work up.
I use small amounts of working solution, so I toss it after use (for example, if I have just a few highlights to do on a print, I start with 10ml of water with 10-20 drops of each stock solution). A liter each of stock lasts a long time
My stock solutions here in Vienna are going on 6 years and doing fine still.
BTW, I use the same bleach for SLIMT contractions and for bleach-redevelopment of negatives when I need that.