If it stays that high, I doubt it needs an accumulator. Does it change height with the button on the dashboard? From my experience with the S55, they sag with bad accumulators. If it doesn't sag and you never see the
Car too low" warning on the dash panel, then I doubt accumulators are the problem. Maybe a valve body rebuild, but flush the system before that. Flush will need $$$$... at least 10 quarts of Pentosin, at minimum 20 bucks a quart, but rebuilding valve bodies is pointless if nasty fluid is in the system carrying grunge all around.
Bad accumulators will pop hydraulic lines. Bad accumulators can also cause the system to throw low pressure codes, too, which many shops will incorrectly interpret as needing to replace the pump. (If the pump has ever been run dry, it must be replaced. If not, leave it be.)
When I got it my S55 would sag after driving for 15 minutes or so, but would come right back up after being parked and allowed to cool down. I did need accumulators, and replacing them removed the sag issue. ABC was still never right, and I got an ABC warning every time I started the car. It always leveled up, but never adjusted while driving, or responded to the height button. I was at the point of giving up on the ABC and throwing on a set of Arnott coilovers when Hurricane Sally took that decision out of my hands.