Resurrecting an old thread to report that I use a home-made toner with about 50g ammonium thiocyanate per liter to tone RC prints, and it keeps at least a day. It didn't work after a week, but I was able to reactivate it by adding some 1% gold chloride solution (of which I use maybe 20-25 ml per session) without adding thiocyanate.
It's a really convenient toner - doesn't smell, not very toxic, single bath, tones in about 5 minutes if the solution is at 100F or so.