Very few boats are fitted with accumulators nowadays. If your boat has been OK for the last 15 years then that would suggest it’s unnecessary. The only problem I had with the “pressure cut out” on Larus was when a piece of plastic swarf got stuck in the flapper valve allowing water to seep backwards reducing the pressure on the delivery side of the pump. The pump would cut in about every 2 mins!! It was fine once I removed the swarf. The pump finally packed up when the housing between the inlet and outlet chambers cracked allowing backflow. The crack was caused by a small amount of water left in the bottom of the pump freezing over winter despite me draining it (you must drain the pump at lay-up if the boat is out of the water). The new pump from Jabsco was an improved design which allowed complete draining. The only snag fitting it was that the fixing holes on the new pump didn’t match the old ones. A bit of improvisation with a piece of plywood was necessary.
I think the answer to your question about the accumulator is “not necessary”.