Don't hang your hat on always having online access to the forms ... you should always save at least a paper copy of the return itself only (not all the backup worksheets) and/or save a PDF in at least 2 places.
See this TurboTax support FAQ for accessing prior year online tax returns - https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/01/270...
If you used the desktop CD/Download editions installed on your computer, the only copy of your tax data file and any PDF's will be on the computer where the return was created. TurboTax does not store online any returns completed using the desktop editions.
And...TurboTax does not have images or copies of any of your income documents like your W-2's or 1099's. Only the data that you entered is stored. You have to save your own copies of those documents, On a daily basis we get people asking for copies of W-2's---and TT does not have them.
SAVE YOUR TAX RETURN !
EVERY year before mid-October you should save a copy of your tax return as a pdf and print a copy of it for your records. That way you will not be searching online frantically when you need it for a lender, FAFSA forms, your next tax return, etc.