When bulk emailing to the forum members, I note it states how many emails you can send per cycle. How long does a cycle last? Let's say I put out 100 per cycle...how many emails would that send per hour?

A cycle is more or less each time the bulk mailer is run based on board activity.

The board activity dynamically activates the system scheduler which in turn runs the bulk mailer a cycle (when it gets a chance). Leave it at the recommended 20, as higher numbers can cause unwanted problems.

my board has 300 member i set mine to 50 at a cycle mass mail finish sending 296 emails in 20mins i was pleased with that.