LW has always had problems with external drives in my experience. That's why I gave up on the concept. Other p2p programs seem to be able to use external drives much more efficiently.

And yes, if your drive is offline when LW starts up then the library preferences will wipe clean all record of such drives & their files. LW in my experience seems to have problems reading from such drives & remembering them.

I share a lot of files, but they are on internal drives. I have four internal 1 GB drives so that's plenty. Plus a lot of ram & cpu power to cope with them.