I like a firm mattress also... I hate squishy dippy saggy mattresses, I used to sleep on this antique bed when I was a kid ...when I would stay at my grandparents place.
Lovely looking bed.... visual wise...was a king single, I felt like a princess in it, but OMG...I think the mattress was stuffed with corn kernels or lentils...that's what it felt like....hmm
... I have always had a thing about creases in sheets on beds, this and or lumpy mattresses, dry feet and pillows.