FWIW, and in case this might help anyone else, I keep a dedicated external hard drive for storing applications.  I started doing this after the Adobe switch to subscriptions and it started as just an Applications folder on my hard drive, then I later moved it to its own external drive.

On the drive, I have directories/folders for software vendors with individual directories/folders inside for their applications.  I keep copies of installers, instructions, patches, upgrades, etc. in there so everything is readily available.  Also I try to keep a text file for each application with purchase info, license info, special instructions, etc.  I also have a master spreadsheet where I keep a list of all my applications, along with the license or activation codes (when applicable), purchase date, purchase price, whether it was a full version or upgrade purchase, initial install date, system requirements, OS compatibility and so on.

Granted, it's not as up to date as it should be and I still have some software obtained the past the year that needs to be added, but basically my goal is to keep everything in one place so I can easily get to them when and if needed.