The recommended approach to extend the evaluation period is to issue a new key that has a permanent expiry date.
For example, to extend an evaluation period by 1 month, assuming today is August 5 2007, create a license key as follows:
(x) Evaluation License
[ ] Expires --- days after installation
[x] Expires on September 5 2007
Note that QLM stores the date of the first call to the ValidateLicense API. This date is never reset. This is by design to prevent users from uninstalling and reinstalling your software to reset their trial period. The drawback of this approach is that the only way to extend a license key is by issuing a key with a permanent expiry date instead of a duration as shown above.
As of QLM 5, you can now extend evaluation keys by sending the customer a new license key with a new duration. The date information stored after the first call to ValidateLicense is now license key specific. So each license key starts a new trial period.