I am assuming that the 18 custom presets in the library will work the same on my new XH A1s as they would on an XH A1 that was manufactured 3 years ago. Is that a safe assumption ?

Yes, in fact your A1s will actually momentarily display the preset name whereas the A1 will only show the preset number.

Not only that, but they're also fully compatible with XL H1A / H1S presets as well.

Thanks guys. I am glad I joined this group. M.D.

Not only that, but they're also fully compatible with XL H1A / H1S presets as well.

Chris, have you tried it? I've loaded the Presets into the XL version of the editor and I get errors.

I can't speak to the third-party preset editor software application, but according to Canon USA, a preset created on an older XL H1 and saved to memory card can then be read, transferred and used by the newer XH A1S / XH G1S (no software editor involved).