Create New Cert for STS. (Need to extend Validity period)

I have an STS and a .NET application. Currently, everything is running smoothly as normal. I noticed that the default STS Cert created only have a 1 year validity period. I was wondering if anybody knew how I could go about extending this time period?
I have tried to create a new self-signed cert through my 2008 Server R2s IIS. This went smoothly but when I tried to update my STS App settings it began throwing an error
My STS keys:
<add key="IssuerName" value="[Value MMC Displays as Issuer]" /> <add key="SigningCertificateName" value="CN=[Value MMC Displays as Issuer]" /> <add key="EncryptingCertificateName" value="/" />
I also updated my applications web.config:

<trustedIssuers> <add thumbprint="??[Value MMC Displays as new thumbprint]" name="STSAPP loca ...