This benefit as well as others are detailed on the Autodesk Subscription web site and in the Subscription Program Guide which should have been included in your subscription welcome kit. So if you upgraded AutoCAD 2002 to AutoCAD 2005 on subscription, you can continue to use your AutoCAD 2002 seats as well as the AutoCAD 2005. At $420 for AutoCAD subscription it is a real bargain and cheaper than upgrading each year on 12 month upgrade cycles especially when you consider the other benefits such as web support and e-Learning content.
Autodesk® Subscription is the best way to stay current with the latest design technology-while gaining the benefits of simplified software management, easy budgeting, e-Learning, and web support.
For a fixed annual fee, you get access to software enhancements that keep your design tools up-to-date and make the most of your investment. Autodesk Subscription includes the following at no additional charge:
Access to all upgrades released during the subscription term Download of extensions for products under subscription Use of e-Learning lessons and knowledge assessments Web support for your Autodesk products under subscription (if included in your contract; not available for 3ds max) Use of previous version of software after an upgrade has been issued Access to the members-only Subscription Center Subscription contract administration tools
http://www.autodesk.com/subscription
Cheers,
-Shaan