emonHub interval vs Feed interval

As I am using a metered internet connection, minimizing data volume going to emonCMS.org is critical. In emonhub I have the interval for sending bulk data to emoncms.org set to 30 seconds. The feed is collecting data every 10 seconds.

My first question is, will I lower my internet data usage by lengthening the emonhub interval to 3600 seconds (once an hour) or will the data usage be the same regardless of the emonhub interval? My assumption is it should be as I will only be consuming http overhead messaging once an hour vs once every 30 seconds (1:120 ratio).

Secondly, I did try setting the interval to every 6 hours (21600 seconds), but I did not receive any data in emoncms.org when setting the interval this wide. Is there an interval limit that I am not aware of?