Yes, while storing content in Walrus, you need to specify the number of epochs for which the content should be stored. The maximum number of epochs is currently 53, which A corresponds to two years. If you want to store it for the longest time possible, you can use the --epochs max command option when storing the blob. You would need to renew or extend the blob's epoch periodically before it expires to ensure it stays stored on Walrus. Once the epoch expires and isn't renewed, the blob gets deleted.