I had a VAX Powa 4000 which did gave around 30 years of service before failing, and for the life of me I can't remember why it failed. I know the pump feature (used for eg carpet washing) failed, but I didn't do that much carpet cleaning. I've now replaced it by what appears to be an almost exact equivalent, still by VAX.
The original VAX was excellent in that although it had a corrugated tube, it never seemed to block up regardless of what was thrown at it – stones, water, swarf, earth, wood, etc. Unfortunately, over the years the original tube & handle broke so I bought a pattern replacement which wasn't as good as the handle part contained ledges which acted to stop stuff going through, so that might be worth being careful about. Indeed, I eventually removed the retaining ring that held the tube to the handle so that I could easily dismantle it for cleaning. This meant that the device relied on suction to hold the parts together when using it.
I have seen other cylinder vacs which the owners have failed to keep clean: they then moan about loss of suction!
Peter G. Shaw