A neighbor of mine has had a Rainbow D2 since around 1977-78 and is still using it today. Was just talking to her about it here the other day.
She says the big deal at the time was that it resembled R2D2,,the little robot from Star Wars!
She also said that the key to using it is to NOT clean too long with any one filling of water. She always stops after about 15-20 min of vacuuming,empties and refills the water pan. Also not storing the rainbow on the pan is important, and of course cleaning out, rinsing out, and towel drying the pan is a good idea. You also want to remove the seperator every few months and scrub it clean with a tooth brush. Infact, Rexair used to supply a special brush with the attachment kit, just for that purpose. My neighbor said she has always run her seperator thru the dishwasher every once in awhile,,and never had a problem.
I agree that this is maybe why the machine is still going strong after all these years.
I will have to say,,her house is VERY dust free,and always smells fresh and clean.
She said that she has had to have a new PN motor once, and has gone thru a couple of brush rolls and hoses,and did have to buy a new water pan once, and one of the clamps that clamps the motor onto the water pan broke off and was repaired,,but other than that, her D2 Rainbow is still going strong. One thing she said she noticed tho is that the cord and plug are now getting hot after running the Rainbow,,probablly time for a new cord.