I agree with what others have said: seasoning some new developer with a couple of sheets is better than nothing but not as good as saving some well-worked developer. But you have to start somewhere; they don't sell Old Brown....wait, I smell a marketing ploy here...anyway, what I do is routinely leave my tray of lith developer sit in the darkroom after I have finished a session. Next day (or next time back in the darkroom) it will have heavily oxidized as well as having been worn out from the printing session. It takes on a lovely color that reminds me of the tannin-rich river water in Michigan's UP. I top off my old brown bottle with this for the next session.