upgrade without replacing?

We are still using 1.3.12 because it has been meeting our needs and we have been reluctant to go through learning how to use the new software. However, recent problems with lost files are making us reconsider upgrading. If we download the current version, is the old version overwritten automatically, or can we keep it as a fallback in case the learning curve proves to be too steep. We are on Mac OS 10.8.5.

I’ve gotten away with installing Audacity in its own Application folder.
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You can get in minor trouble with plugins like that (too many), but for the most part it works.

There is also a “Portable” technique where the installs are completely separate. I’ve never done that.