Yes andreios, gold is lovely, but too pricey.
Adelorenzo, I used to overexpose the print, but recently it hasn't been necessary. I use a very dilute solution, 1:400. My paper is also acidified with sulfamic acid... but not sure if this helps prevent bleaching.
My normal selenium toning solution (for fiber paper) is much stronger, so that may explain it. I'll try something more diluted next time and see if the bleaching effect is reduced.