What is it that determines how far one can be … battery power, specific models of keyboard, “muscleness” of the wireless system, … ?
Bluetooth wireless has a range of about 30 feet. At around that limit my wireless mouse is quite laggy, but combined with Cubase iC it does the trick. You can buy a bluetooth usb dongle which may give you an extra 10 feet or so on the end of a usb cable, but usb cables have a limited length as well. I would imagine that it also depends on how much junk the signal has to get past-ie appliances, walls full of plumbing and electrical boxes, etc. In my case the five feet of iso booth can kill the connection so placing it on the wall closest to the transmitter makes all the difference.