Certainly very early telescopic shock absorbers, specifically Newtons have no wearing parts other than seals. The metal bits are surrounded by oil and use the oil as a damping medium, so the oil 'wears out' but not really the structure. I've refurbished two circa 1930 Newtons and it was quite straightforward to do.
Gas shockers actually use gas and oil, and I guess mechanically, not the sort of thing one could re-condition at home.
