BTW: I have heard from at least one seller of libraries that one of the main reasons for creating libraries not bigger than 128MB is that they can be "quickly previewed" in the Motif's 128MB of RAM. It also depends on the type of library: A nice 8 layer piano or rhodes alone takes much more than 128MB (and as you can see -using the example of Korg Kronos and EXS libraries-, with growing user memory, libraries tend to get bigger and probably better:
https://shop.korg.com/kronosSoundLibraries). Let's say, I want to load K-Sounds Epic Grand (500MB, 16 bit linear), Chicks Mark V (400MB, WXC compressed), DSF Symphonic Strings (450MB), then there is not much memory left for e.g. a good amount of wav files for backing tracks. I find that quite limiting in the year 2016