do you not reclaim your potting soil, Cat? Like you, I also mix my own soil. When it is done (or a plant is male or hermie and needs to die) the soil goes into a large tote. To this I'll add some vegetable scraps, peanut shells and compost starter. Then it's ready to use for the next grow. I just test the soil for nutrients and add a little new peat, perlite and whatever I think it needs.