If you open/load a folder with loats of font inside it, it takes some time, to be fully shown, if you have the WYSIWYG option turned on. That’s OK for the first time, but if someone needs, to activate another font from that folder and he closed the application, MainType needs, to reload all these fonts. And without caching, this can be sometimes quite painfull.
Recent versions of MainType use a database which makes finding fonts much faster.