I have the understanding that when you switch from perpetual to maintenance you are required to give up your perpetual license and uninstall from your device(s). Thus if you do not pay you cannot access you files because you have no access to the software.

If you keep your perpetual license until Autodesk breaks their contract by not allowing you access to updates then you can keep your copy running until you device dies or you upgrade. There is no way Autodesk can support you and your archaic licensing system when they are having such a financial hardship with the record profits they reported this year.

As a user from the Wavefront days I have seen enough and will Keep my perpetual license and my money away from Autodesk