Good grief, what next.
My motorcycle gets an oil change and general once over very 2 or 3 months. The mirrors, seat, and other functional parts get a dust off as required, but it has only been cleaned once in the 10 years I have owned it. That was when the mechanic had a quiet day and wanted something to do.
My Mac Mini had RAM upgrade and a general clean on the inside after I had owned it for about 3 years, and might get the same come 6 years, next year. Outside, it just gets a dust when I disconnect it to take to work on the odd occasion.
I don't know why people are so concerned about keeping things pristine. The "Show us your Mac" thread pictures all look like the charlady just left.
I reckon things are far more interesting if they look like they are being used, and bear the scars of day to day life.