I contacted MS Support and it was explained that this is by design.
First, I was incorrect in my changed lease time . . . it was not 4 hours, it was an hour. This is applied by the MCLT (maximum client lead time) from the failover server. Here is the link, which describes the behavior:
Google dn338973 DHCP Failover Examples
The 1 hour lease time was applied because we performed an ipconfig /release & renew. Had we then performed an ipconfig /renew once again, the correct lease period would have been applied to the client. If we had waited about 30 minutes (50%
of the lease time or more), it would have updated and reflected the lease time configured in the scope automagically.
I hope this post helps someone else out!
K. Richie