I have two options when such information is not listed. 1) PM the developer or 2) Search through the discussion section to see if it's stated there. In both cases I have to keep track(side notes) so I can compare the total cost to other add-ons. And if the developers decides to change his policies I only find out when it's too late.
Developers, please do me a personal favor and include your policies regarding extended upgrades and Support in the overview of your paid resources.