Currently Emerson does not have a way to make a cert longer than 90 days if you do not do it during the initial installation........
Using powershell you can clone the existing cert and then extend it as long as you wish. Using a self signed cert does come with some risks and you should do an assessment as to which kind of cert will best serve you and your plant. You will need to go in to IIS afterwards and assign the new cert once complete. The new cert will also have to be imported on all of the machines/devices that used the original cert.
This will list the thumbprints of the certs. You will need to identify and copy the one from the 90 cert. I find it better to copy and paste the value than type it in. You can verify which one is correct by examining your current cert. This is by no means the best way it is just the one that I came up with and worked for me. I attempted to make a new cert from scratch but there were a few settings I had difficulty with and ultimately cloning the working one gave me immediate success.
PS C:\>Get-ChildItem -path cert:\LocalMachine\My
Set the file path
PS C:\> Set-Location -Path "cert:\LocalMachine\My"
Assign the old cert to a variable $oldcert. Need to paste in the thumbprint of the current cert.
PS Cert:\LocalMachine\My> $OldCert = (Get-ChildItem -Path "thumbprint of 90 day cert")
This will generate the new cert based off of the old one with a ten year expiration. You will also see the new thumbprint which you will need later Below makes a 1 year cert but you can make it longer.
PS Cert:\LocalMachine\My> New-SelfSignedCertificate -CloneCert $OldCert -NotAfter (Get-Date).AddYears(1)
Store a password for the cert to be exported. (change YourPassword)
PS Cert:\LocalMachine\My>$CertPassword = ConvertTo-SecureString -String “YourPassword” -Force –AsPlainText
Exporting the new cert to the C drive. Need to paste the thumbprint of the new cert in the command
PS Cert:\LocalMachine\My>Export-PfxCertificate -Cert cert:\LocalMachine\My\"thumbprint of new cert" -FilePath C:\cert_name.pfx -Password $CertPassword
After this you will need to import the cert to the trusted root using the password assigned in the process.
Hope this helps some people out.