Knickers and socks daily, bras/nighties every other day. Jeans/trousers probably every 4/5 wears. T-shirts every 2 wears. Jumpers every 4/5 wears, cardigans probably less frequently because I wear them over a blouse on warmer days and they're likely not kept on all day.
In summer lightweight cotton trousers and tees tend to get washed every day.
DH is pretty much the same as me.
The PiL used to stay with us from time to time, usually a long weekend from Friday to Monday. One Saturday I was putting some washing on and asked MiL if she wanted anything washed, and she brought down her undies and tights. What about Dad's undies?, I said. Oh no, they're OK, she said, he's just changed them - he puts clean ones on every Friday
. I never asked again.