The issue with load times is three fold, at least as far as Gen4 are concerned.
1) Poser content has never been compatible with DS, it has to be dragged in through an importer plugin, which converts Posers ancient rigging into a crippled WM rig.
2) When DAZ were designing the Gen4 family, they knew they would end up releasing even more updated CR2’s than they ever released for the Gen 3’s, so they created the EXP system so they wouldn’t have to. Problem is they also got it into their thick skulls, that loading hundreds or thousands of little small files was better than loading one or two big files, it isn’t as it’s as slow as ****, which is why virtually nobody outside of DAZ used it.
3) While DS1, 2 & 3 were designed around Poser content, DS4 wasn’t, it’s designed purely for Genesis, so not only does DS have to convert Poser content as in 1 above but it also has to convert it to work similar to Genesis (ie single skin mesh with all of the morphs hidden in the BODY, with ERC’d ghost dials in the body parts).
With 4.5 you are actually better off loading all of your Poser content into an empty scene, and then saving each item as a scene subset, in the case of V4.2 you should INJect all of her DAZ morphs before you save her, and load those DUF files instead of the Poser files. They don’t take as long to load that way, or have a large RAM hit as none of the deltas will get loaded until you spin a dial.