Tossing them throws them into the landfill in a concentrated state. And wastes money :-) As I switched, I kept my older stuff and used it occasionally, to compare and remind myself that the new stuff was just as good, or at times when the new stuff didn't quite do the job. I've got a new spray cleaner that does 97% of the cleaning I need to do, but the less natural one is still useful for that rare 3%.