I would think it would be ok, as long as the cuttings and/or seeds you had in there didn't develop some kind of disease or anything. I mean, I know they say it has to be a sterile environment, but hey, the vast vast vast majority of seeds in the world get started right out in the nasty, messy world. I'd give it a try, as long as you'd be ok with it if it didn't work out. Maybe do some in the old mix, some in the new?

You can always mix it with regular potting soil to pot up more mature plants too. I would use it again, even for sticking cuttings or planting seeds.

Janie

Also, if you're truly worried about it, you can place it in your oven and "re-sterilize" it.

Here is a link that might be useful: This contains 4 methods of sterilizing soil