I can think of much better ways for P&O to increase their spending on passengers, than to change the bed sheets more than once a week. Although I am intrigued as to which nocturnal activities Ardennais does on holiday, that needs regular fresh sheets.
If there is extra money, let's have an improvement in food choice and quality, in the MDR, and lunch and evening buffet, much more worthwhile than an extra bed linen change.