I answered your other question and think you will benefit from switching to time-based indices. This allows a smaller set of indices to be targeted if you are only looking at data within a limited time frame.
The ideal time period an index should cover varies by use case. Adjust the number of primary shard based on the number of nodes in the cluster (to spread data out) as well as volume indexed per day. Make sure you do not end up with too small or too large shards. Having large number of very small shards is inefficient as each shard has some overhead and too large shards can affect query performance as well as recovery.