1. It don't need to be open. Just wait some days and then open it.

2. You must have a large amount of ESP and must be consolidated in one or two large chunks, or you will wait for a long time. It works like the hashing power in mining. The hashing power in our case is the number of ESP multiplied by the time we leave them unused in our wallet.

For example, my 50 million chunk of ESP gave me about 40 thousand more after one and a half days.
After they mature, i send them to myself to consolidate them (combine them in one chunk) and then i wait another one and a half days or more. The more time i wait, the more are the changes to get the reward soon after i open the wallet.