I completely understand, using a vacuum like that can really be hard on your back. However, installing a system like this afterward is definitely not easy; it should always be planned during the construction phase. This is because it requires considerable work due to the pipes inside the walls!
I also quickly got tired of carrying the vacuum cleaner up and down the stairs all the time. Since installing a central vacuum system was no longer an option for me, I bought a second vacuum cleaner. One stays upstairs and one downstairs, so I can vacuum everywhere, and that was cheaper than a central vacuum system!