Well, this is not QlikView related, so you might get better help in a more appropriate forum.
From what I understand, in general you cannot change the expiry date, you'll need to re-issue a new certificate.
Regarding to expiry date, when you open the website in your browser, click on the padlock icon and select view certificates. It should show you the start and end date.
There is a utility called SELFSSL that is part of the IIS6 resource tools.
The command line for this would be like selfssl.exe /N:CN=LAB10 /K:2048 /V:3650
where K=KeyLength V=number of day the certificate is valid.
selfssl.exe /? will give you the switches
Oh, more thing the error Ignore the Error opening metabase: 0x80040154