I have created a form and saved it as a PDF. None of the interactive features will be needed. Right now it's the only form I need, so I don't envision a paid subscription. How long can I retain my one form for revision. Can I change the dates or edit it for this time next year?
Your form is retained in your account until you delete it yourself, there is no "expiration" or time out.
Just a note: I am guessing since you mention saving to PDF that you might be using the "FormsCentral Desktop" application that is included with Acrobat Pro XI, if that is the case, you can have one form "online" when you are signed into FormCentral with a Free account, but you can also have unlimited "local" forms in the Desktop application, those "local" forms would only appear in your desktop application and not if you signed into FormsCentral from another computer or web browser.