TL;DR: Unless you're shooting 25k+ shots per year, skip all this nonsense and just use one monolithic catalog. There used to be a performance benefit to fragmenting catalogs like this, but the advantages are small in modern LR. Otherwise, see below.

In your proposed methodology, you've correctly deduced that you will lose quality due to applying multiple sequential .jpeg compression operations. Importantly, I think you'll still encounter repeat .jpeg compression even if you export using the Original option for file format - how else would Lightroom apply any adjustments to the file? It may be smart enough to export an unmodified copy if there are no adjustments, but I wouldn't count on that. You could check this by comparing the md5 hash of the twice-exported .jpeg vs. the once-exported .jpeg.

You could avoid this by manually copying the .jpeg from its location on disk to your desired export location, but there's a much better way. What you actually want to do instead is to export a catalog of the selects from each year, rather than exporting photos themselves. See "Export a Catalog" here. You'll want to uncheck the option to export the negative files and previews. Lightroom catalogs can embed the negative files themselves so that you can send one monolithic file, for example to a postprocessing service. In your case, assuming the multi-year catalog exists on the same machine as the individual-year catalogs, you won't need to embed the negative files.

Once you've exported a catalog of selects from each year, you'll want to create your "super catalog" as a new empty catalog and open it. Finally, import each catalog of selects that you exported earlier (see "How do I merge two catalogs or import folders from another catalog?" here). You should now have a catalog of just your selects, and it should already be properly linked against the original raws (run Lightroom's "Check for missing files" to verify).