Finally got a chance to test this code on our domain. I have two accounts

1) Account#1 is a Domain Admin account that DOES have an expiry

2) Account#2 is a Domain User account that DOES NOT have an expiry

Running as Account#2 (the Domain User) - if I query my own ExpiryDate (should be none) - I get the following error:

COM exception error "AccountExpirationDate" ((null) - (null)) [-2147352567/80020
009]

So I guess this error means there is no expiry date. And you can test for it. However, if I query the status of my Domain Admin account - still running as Account#2 (Domain User) mind you, I get the following:

Your account expires on 11/1/2007

So it looks like it works ok - querying ExpiryDate as a normal user that is.