Yes, I do the same. Best to keep data on a dedicated drive imo and a NAS box can be kept off the desk out of harm's way. The challenge with USB and LR is getting the same drive letter assigned every time you connect it - unless someone has found a way of telling LR what the new letter is ????
I re routed one of my PCs (a small HP one, the wife's now) on top of the kitchen cupboards with the Network Drive and modem and router, well out of harms way, I lost an NAS once by knocking it over, very sensitive items, I also have it velcrod to the base unit up there, dont know why they design them upright when they are so sensitive!?? Wires are then routed from there to my main PC, wireless isnt the fastest!
I think I sussed the drive letter out Tim. It always works for me now, It may be a combionation of regular switching which I do, depends where I want to edit, on the macbook or on the desktop.
But I think the main thing is once your hard drive appears on your desktop, rename it to something you recognise (eg Portable HD), it is recognised as that and drive J, everytime I switch now. Months we're talking, and I havent stopped editting lately.
My 1TB NAS is just used as a back up now from Lightroom, all my pics go on the 500GB portable, as well as the Vosonic after every dive day