I have a Windows 2008 OCSP responder that is automatically renewing it's signing certificate (from an Enterprise 2008 CA) every 2 days, despite the template having a lifetime of a year and a renewal period of 6 weeks (yes I know that is considered too long, has to be that way). When the OCSP service was first installed the template had a very short lifetime with a renewal period of two days, however it's subsequently been extended. The provider has been deleted and re-added, but it won't honor the new renewal periods. The CA stopped offering the template, then re added it. In between re-adding an OCSP provider any old certs have been deleted (from the service account). Any ideas what could be happening?

After you edit the template, you have to re-enroll all certificate holders http://technet.microsoft.com/en-us/library/cc771246(WS.10).aspx

Unfortunately that didn't make any difference, still ignoring the values and renewing every two days...

Try setting up the OCSP configuration anew, if you are using autoenroll of the certificate. Think I had a similar thing happen in the lab onetime, though it went away after I configured the OCSP anew. Just a though :)

I've set up the OCSP configuration for this provider many times. The only thing i have left to try is to completely remove the service and install it again, but that seems a little drastic.