The batteries should not degrade that fast.
For real!
I use several refurbished APC UPS’, and also use third-party batteries (from the company that refurbishes the UPS’) and it’s been trouble-free for like 10 years. I replace batteries, it seems, every 4-5 years and only when the self-test says to replace it.
Never had a problem with data loss due to the UPS failure.
I went through the same dilemma. The old Synology photo software had a duplicate finder, but they removed that feature with the “new” version. But even with the duplicate finder, it wasn’t very powerful and offered no adjustability.
In the end, I ended up paying for a program called “Excire Foto”, which can pull images from my NAS, and can not only find duplicates in a customized and accurate way. It also has a localAI search that bests even Google Photos.
It runs from windows, saves its own database, and can be used as read-only, if you only want to make use of the search feature.
To me, it was worth the investment.
Side note: if I only had <50,000 photos, then I’d probably find a free/cheaper way to do it. At the time, I had over 150,000 images, going back to when the first digital cameras were available + hundreds of scanned negatives and traditional (film) photos, so I really didn’t want to spend weeks sorting it all out!
Oh, the software can even tag your photos for subjects so that it’s baked into the EXIF data (so other programs can make use of it).