I currently have a nice 15-20ft bench in my office, but only 5ft of it is actually usable anyway. The rest is permanently piled full of crap. I assume it works out this way because only 5ft of space is actually needed.

In the 'usable' 5ft of bench space, I have room for a Rigol 1052E, stereo microscope, power supply (I have a very narrow extech switching one), and soldering station / fume extractor. There's still plenty of room for my current project under test. Built into my bench are drawers where I store most of my less-used gear -- the big linear power supply, function generator, frequency counter, desoldering iron, hot air iron, etc.
I constructed my bench from a formica countertop and utility cabinets from a local big box hardware store. That worked out pretty well, as I could cut the countertop to size to fit the available space. It can all be torn down and move if need be (and in fact, last time I moved, I did tear it down and move it to the place, adding some additional countertop in the process)
I'm finding that more critical than workspace and test gear space, is space for project storage and component storage. I keep accumulating more stuff.