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You still have to consider the amount of paint you’ll be spraying before you clean it as you waste all the paint in the machine. I don’t have one as I’ve found I’m never faced with an entire house to paint but if you’re prepared to mask everything and paint it all in one go it might be worth it. Newly plastered walls are rarely perfect either so there might be a lot of prep anyway, the prep work and woodwork is the most time consuming aspect of most decorating jobs which is why I still reckon an 18” roller is a good balance between speed and cost.
Airless paint sprayers look like an interesting option. Cleaning looks relatively straightforward as long as you get one with an 'in' pipe which draws directly from a paint can or bucket. £££ though.