It looks like everything is working as normal.  Unless someone out there is getting a better response time on their set up.  The heartbeat is continuous.  Then when it does not get a response from the Master then the Backup takes over the role. Here is some information on Master/Backup relationship on the 55xx series switch. Switching from the Master to the Master Backup The Master Backup replaces the Stack Master if one or more of the following events occur: • The Stack Master fails or is removed from the stack. • Links from the Stack Master to the stacking members fails. • User performs soft switchover via the Web interface or the CLI. Switching between the Stack Master and the Master Backup results in limited service loss. Dynamic tables are relearned if a failure occurs. The Running Configuration file is synchronized between Stack Master and the Master Backup, and continues running on the Master Backup. When a Master fails (or when an Operator requests a switchover between the Master and its Backup), a “switchover” occurs, the Backup master becomes a Master, it restarts all protocols and reconfigures the stack with the configuration it has. There is almost no abruption to the traffic within the stack except that no packets are sent from the stack members to the new stack master until it signals to the stack members that it is ready, thus minimizing the packet loss in case of Master failure. As part of the takeover process, the “new” master erases all tables from the packet processors. These tables are relearned (Dynamic MAC addresses, STP state table).
I was doing some testing here with 2 PC5548 switches, configured as a stack via HDMI in my lab.  Is it correct that in the case of the loss of the master, the secondary will take over, but takes about 45 seconds to do that election?  The results of my testing look a bit like: I'm just wondering if maybe I set something up wrong.  I figured that if I lost or rebooted the master, that the secondary would continue on as redundant, and the 45 seconds seems like a pretty big window.  I'm very willing to find out that I did something incorrectly though.
PC5548 Stacking