Here is an idea for getting buy in from clients or visitors to your website when trying to sell dSS.
Create a installer that will be available for use for 30 days, You can add a tickler to your calendar and then every 60 days recreate a new installer, post to your website with a form to access the download link. Then after 60 days change the config on installer one to uninstall and redirect to a website asking them to subscribe if they want to continue to use the app. Or it just gets uninstalled and you have the contact info on file to market to them in the future.
They would actually get 60 days of use, thinking they pulled one over on you, but this way someone who happens to download the file on the 30 day of the free trial wouldn't get burned for only one day of use.
Going to give it try and let you know how it goes.