There are several approaches to solve this problem. In no particular order, there are several softwares and a way to use OS tools to backup and restore the file associations. I am not affiliated with any of these softwares, just new to Windows 10 and falling down the tree and hitting every branch on the way down. (I have not yet had a chance to test these solutions, but I will be doing so after I post this)
Stop Resetting my Apps
Link: http://www.carifred.com/stop_resetting_my_apps/
Description: As you may have already experienced, Windows 10 may periodically reset the default apps. The reset action usually takes place after a Windows update or an update of one of the Windows built-in apps such as Microsoft Edge, Photos or Groove Music.
Default apps are the programs that are executed by default when you open a file or protocol. Resetting them without your consent can be extremely unconvenient, because it can take a lot of work to set them back again.
Stop Resetting My Apps helps you to work around this issue by preventing some of those built-in apps from being set as the default apps. This does not affect the functionality of those apps. They are simply not listed in the OpenWith menu or in the Default apps Windows settings section.

File Types Manager
Link: http://www.nirsoft.net/utils/file_types_manager.html
Description: FileTypesMan is an alternative to the 'File Types' tab in the 'Folder Options' of Windows. It displays the list of all file extensions and types registered on your computer. For each file type, the following information is displayed: Type Name, Description, MIME Type, Perceived Type, Flags, Browser Flags, and more.
FileTypesMan also allows you to easily edit the properties and flags of each file type, as well as it allows you to add, edit, and remove actions in a file type.

File Association Fixer
Link: http://www.thewindowsclub.com/file-association-fixer-2-windows-10-8-7
Description: If you find that you cannot open a particular file type, then our File Association Fixer v2 for Windows 10 / 8 / 7 will be able to easily help you fix, repair and restore the broken file associations. Broken file associations, are typically caused due to a corrupted Registry. Again the reason for a corrupted registry could be malware or a bad software. As a result of this corruption, your Windows OS is unable to open some files or a particular file type.

Manually Backup/Restore
A Redditor posted a how-to article here explaining the process. There's a different post on this article from Groovy Post. There are also some manual options on this SuperUser Q&A. I came across that Q&A when looking for help; You can't ask for software recommendations there, so i figured I would make an 1-stop-shop Q&A here for recommendations