Don't do that unless you have to though: closed indices are no longer managed by ES. Meaning if a node dies with closed index shards, they will not be recovered elsewhere. Say you close an index for 2 months and you had 2 node failures in that time .. it could just be that both primary and replica shard X were discarded and never recovered. You try to open the index one day and voila: it's Red and you lost data.
Just saying 