I'm a supply teacher, and have been for nearly 5 years.
Nowadays, I no longer surprised to arrive at a school to hear I'm covering Miss X, who is off more than the rest of the staff put together.
Of the 3 schools I visit most recently, 8 times out of 10 it's to cover the same teacher each time, who is off ill.
My friend's DD is in Year 6 and got a teacher who was new to the school in September. That teacher has had 2 long periods of absence, and then a phased return each time. Apparently, the kids feel like she's away more than she's in. And when she's off, the deputy head has to sit in the class, with the supply teacher teaching, because the class are so badly behaved when the usual teacher is off.