How large a garden area does each Subpod service (fertilize?)
If the Subpod is in a raised garden bed, the immediate area (half a foot or 15cm) around the Subpod will be enriched quickly (within several months). Once the Subpod is full (after about 6 months depending on feeding and worms), by sprinkling the castings through the bed, you will enrich the entire bed. The larger the bed the more gradual the process for the entire bed to be enriched.
For a single Subpod, this will work well for a raised garden bed of up to 3 feet/90 cm by 5 feet/150 cm feet. For larger beds with a single Subpod, the best approach is to sprinkle castings around individual plants in the bed when emptying the full Subpod of castings.