I had created my custom solution which is set custom master page onfeature activation and remove custom master page and set default master page as it is on feature deactivation.
I have developed this solution. the problem is that I want to allow this facility for trial version for any user.
Ex. If I have deploy this solution for any site then it will expire in 30 days. after that it will ask for license key to user.
How should I do this?