Hi Dave,
One way you can look at the uptime of the CIMC is by collecting the cimc logs. Once you get this file you need to extract it. Under the "temp" folder open the tech_support file. In this file do a search for "uptime"
If you don't know how to collect the logs see link below.
http://www.cisco.com/c/en/us/support/docs/servers-unified-computing/ucs-c200-m1-high-density-rack-mount-server/111508-tshoot-tips-cimc.html