To be honest, I've never tried... I've always just made the assumption they would be no good.
I guess ultimately it depends on their condition. Usually I give my seeds two or three months before I declare them failed (call me an optimist
)... and by that stage, the pellet can look utterly worse for wear. They seem to eventually get this hardness to them regardless of how moist they are. I don't like the idea of the old rotten seeds being in there either.
How old were the ones you reused and what condition were they in? I'm curious now... and wondering if I can't save myself a buck or two in the future!