When I was selling my condo so I could buy a house, one of the first things the realtor said was that my condo, which was well laid-out, looked cramped and crowded, and suggested I remove several large pieces of furniture to make it more saleable. I contacted one of the companies that has the moveable pods, which picks up and delivers, and they came out, carried all the stuff down the stairs, packed it carefully into the pod and stored it at their facility until I sold the condo and moved - at which point they delivered the pod to my new house, unloaded it, and left.
This had a several advantages. The pod is cheaper than a storage unit, it was still accessible (I had to call the day before - they store the pods in stacks, so they needed notice to get it out), and they picked up and delivered - which was both easier than moving my grandmother's dining room set down the stairs myself, and cheaper than a moving service.
If you're in a situation where you are between homes and want to hang on to your stuff - get a storage unit or a pod. If you've run out of room and aren't moving soon - it's time to weed your belongings. When we moved my grandfather into the retirement community, we had to clean out 50 years worth of stuff he'd hung on to "in case he needed it" - we had to rent a moving van to go to Goodwill, and hire a truck and driver to take the rest of it to the dump (the nearest available dump was over 100 miles away - so the truck and driver ended up cheaper than doing it ourselves). Having helped clean out his house - I clean mine out every year, and still keep finding things... not helped by the fact that my mother's method of cleaning her house is to give everything to me, so she doesn't have to throw it out.