I recently had a problem with my Miele washing machine leaking badly. After 15 years I thought maybe it is rusted...but no, they do not rust as easily as cheap machines, and it has a hose that was leaking.
It had a huge build up of calcium and the mechanic put descaler through the machine and advised that the dishwasher should also have it done.
I always do my coffee machine as that automatically tells me when it is time to do it, and I do my kettle regularly as it gets white on the bottom which I dont like the look of.
Some waters are not as bad as ours I believe so not sure if everyone has to do this.
My washing machine is fine now and should go on for another 10 - 15 years though I will descale it more than once in 15 years from now on.
I was advised by my washing machine service tech to use vinegar in my fabric softener receptical. It helps rinse the clothes and cleans the machine. If your clothers come out smelling like vinegar the smell will go when dry , just use less next time.