Originally Posted by gr82bart
Theoreticaly the PO doesn't go bad like silver gelatin paper developer. Over time it will accumulate palladium which will 'season' the developer which will change the developer characteristics some. Eventually it will become quite murky. At that point you may want to decant the developer to remove some of the sludge and replinish with fresh potassium oxalate.
As for the sponge brush I would replace that as soon as you can with a Richeson 9010 brush, a.k.a. the magic brush. The sponge brush abrades the paper surface raising the nap. The Richeson coats very smoothly and doesn't abraid the paper. You can also use a glass rod, a.k.a. 'puddle pusher'. It will coat much smoother than a sponge brush but the magic brush is the champ. I'm not sure what a camel hair brush is or how it would work so I can't comment on that.