If you want edit-ability, the native file format always wins. Programs all work better in their native format. Sometimes things can be lost, like groups, transformations, gradients, metadata, layers, ect when exporting. If you just wanted to export to another location so you had better thumbnails, that is fine, disc space is cheap. I would think converting them all and not keeping the native format to be real bad.
I keep all artwork I create in its native format. Art work I have found elsewhere I keep most of the time in the format I found it. Converting can cause data loss like I mentioned above. I even keep a back up of my artwork based on revision. A program backs up a time stamped-named file to another location each time I save the file. If I just relied on exports, I would have know way of replicating an earlier stage with reliability. Maybe you just need better thumbnails.
Sage Thumbs is a windows program that does ok at adding eps and other thumbnails to windows explorer. I think it requires ghostscript be installed and in order.
https://www.cherubicsoft.com/en/projects/sagethumbs
If you have CorelDraw, a program called ST Thumbnails Explorer is the best thumbnail viewer I have found. It finds the installed CoreDraw and uses its engine to generate the thumbnails and also uses ghostscript. I said it is the best not in its appearance or function, but best in that it handles almost every vector format. It's just about the only one that makes reliable CDR thumbnails, but handles practically all the ones I've thrown at it, except for maybe a CAD like one or two.
Xnview and XnviewMP are two others that do well. XnView is their classic viewer and XnViewMP their updated one. They also make the above SageThumbs.
https://www.xnview.com/en/
Ghostscript is need for those for AI EPS and PDF.
https://www.ghostscript.com
Here is a Windows Explorer screen shot. With SageThumbs installed you can see eps ai svg and other formats just fine.