In IIS, we can create a self-signed certificate. The expiration of the certificate defaults to one year. Does anyone know whether this can be changed for example via the "Configuration Editor"?
IIS doesn't do anything special when generating a self-signed certificate so you can use and tool for that.
For instance, you can use Powershell. This one-liner will create a self-signed certificate for the DNS name
test valid for 5 years, with no password and place it into the local machine certificate store (it requires elevation).
New-SelfSignedCertificate -DnsName "test" -notAfter $([datetime]::now.AddYears(5)) -CertStoreLocation cert:\Localmachin\My