Question regarding template_overwrite in logstash output to elasticsearch

I want to do the on the fly template overwrite for 1 of my index data (basically is to decrease the shards count). so i need to add below session:
my questions is do I need to add this to all the logstash indexer's conf which output to same index or only need to add into one? my thought is add into one should be enough because once the template is overwritten (by either of the indexer), the rest of indexer will use the new template already. Please correct me if I am wrong.

output {
elasticsearch {
hosts => ["fslelkprod01","fslelkprod02","fslelkprod03"]
index => "amhstrending-%{+YYYY.MM.dd}"
template => "/etc/logstash/template/amhstrending_template.json"
template_overwrite => true

my template file is very simple actually:

"template" : "amhstrending-*",
"settings" : {
"number_of_shards" : "1",
"number_of_replicas" : "0"

Putting in one should be ok, has the template been uploaded to ES?

yes I can see the template uploaded successfully.

hi Mark,
I see something interesting, the template change only last for 1 day. next day the data will still process by the original shark no. and _template changed in previous day gone also.