Implementing Trial to Purchase

I have been reading the forums trying to find my answers and it appears that the best method to go from customer download of a trial to purchase is to issue a license with fixed number of days as a trial. This is where I'm confused. Under Edit version Details, it has Trial Length (in Days). Should I leave this at '0', and use a license field is_trial, set it to true and use another license field expires_on and set it for the date of NOW + 14 days when I request the license from LimeLM? In the Fastspring PHP script, can't I simply request 14 day trial License? Can the TRIAL LENGTH (in days) be set from the Fastspring PHP and is the best way to issue back to fastspring a license that is restricted to run for only 14 days? After 14 days the trial stops. Suggestions appreciated.

When a customer purchases, they get 1 year of updates/support etc... I will need to issue another License Key, I'm assuming. Should I date stamp 'expires_on' (NOW + 1 year) in the PHP when the licensed is purchased at Fastspring. So now I will need to check to see if the license is genuine and that the license has not expired each time my software is loaded? If expired, then warn they no longer get updates. Set a my.settings.NoUpdates = True and then no longer bother the customer regarding licensing. If 'expires_on is greater than NOW, then run the software. Correct?

I appreciate all your quick responses! They have been very helpful. I'm almost done getting my head around this and implementing. FastSpring and the PHP is working great! Trying to find the best way of handling.

Also, if a 14 day trial license has expired, or I issue a new license, I'm assuming this counts as an allocated activation on my user account. These trial licenses could possibly eat up my available licenses very quickly?? Please let me know how that is handled if I could deleted these short term trial licenses?