You don't need to take it in every 4-5 years unless you're lazy at maintenance, suck up ash, drywall, leave it on a wet basin and never clean the separator. Selling these I could tell you there are countless unserviced D4s still around. If it were me, given the cost of a new one, I might take it in every 10 years, the cost of service isn't bad at least here. You'll still come out way ahead and way cleaner than the $60 vacuum every 6 months crowd. The newest Rainbow is amazing, I've demoed it against Dysons, Kirbys, Central Vacs, cheap stuff, you'd be amazed. If you stick your hand by the Rainbow power head you really feel air moving, a lot, with a lot of vacs you don't feel anywhere near as much, often times more turbulence from the brush roller. Until you do it yourself you can't describe it, but if you combine it with a good powerhead, and I think their current is amongst the best canister powerheads I've used, the results are really good. Personally I'd never have bought one without trying it, I acquired an E Series when it was a current model from a thrift store, eventually, though it took a while, my wife and I realized it did do what is said, and despite the water being slightly inconvenient, the house always smells clean and it didn't upset her asthma. Now with 3 Rainbows, one for each level of the house, they are used primarily, Dysons and Fantoms used for quick jobs (taking the wear off the Fantoms doesn't bother me). The water becomes no harder than emptying the bin, adding 2 or 3 minutes to the vacuuming experience. If you're maintaining it well pull the HEPA after a few months, if you're following the recommendations it will look brand new. Don't leave the water in too long, don't use too little, clean the separator, it isn't hard. Those who say water isn't a good filter medium fail to realize the separator itself was designed to spin the dirt out without water. They say water only traps 60% of the dirt due to the bubbles, but they don't realize the separator slings the dirt back into the bubbling water bath. Others can make similar machines these days, Rainbow's biggest advantages are in motor and powerhead design. Sure they're expensive but at least they are USA made.