How long are old versions of Turbotax, that I purchased in the past, available for download?

They only support the last 3 years of programs.  If you bought the downloads log into your account and see.  I wouldn't uninstall them.  If you install an older year you won't be able to update it or download any state programs you need.   Have you been saving the pdf files each year?   

Once you have filed successfully … you can shut off the auto updater function and then save the return &  .taxfile.

For Windows, up in the top menu, you  can set the  "Updater Preferences" to "Always Ask" or more commonly set to "I don't have an internet connection"  (even if you do), and then you are not forced to update....and can manually force an update when you choose to do so.   And then you can open the file(s) at any time with no forced upgrade.

But that's the Windows software.....not a MAC. For a MAC you cannot turn off the auto updater  HOWEVER  you can simply disconnect from the internet before opening the tax return.

It's always a good idea to make a backup copy of your tax data file, in case your original gets lost or corrupted. Here's how:

1. From the File menu in the upper-left corner of TurboTax, choose Save As (Windows) or Save (Mac).
2. Browse to where you want to save your backup.
   • Tip: If you're saving to a portable device, save it to your computer first to prevent data corruption. Then, after completing Step 4, copy or move the backup file to your device.
3. In the File name field, enter a name that will distinguish it from the original tax file (for example, add "Backup" or "Copy" to the file name)
4. Click Save and then close TurboTax.
5. Restart TurboTax and open the backup copy to make sure it's not corrupted. If you get an error, delete the backup and repeat these steps.

If you make changes to your original tax return file, repeat these steps to ensure your original and backup copies are in-synch.

Related Information:                             

• Retrieve a Tax File from a Portable Device
• What's the difference between the tax data file and the PDF file?

AND save it as a PDF so you have access to a copy even if you don’t have the program still installed and operational :

• How do I save my return as a PDF in the TurboTax software for Windows?
• How do I save my return as a PDF in the TurboTax software for Mac?

AND protect the files :

• How can I protect the tax files on my computer?

make paper copies of old tax returns.

You can also write PDF copies to a DVD if you have a DVD writer, or,

to cloud storage.

Then, you can uninstall those programs.