Shower: how often is enough?

I have a flatmate who takes a shower every 5 days. He has a strong BO - he takes a shower in the morning, and by the end of the day he starts to smell sweaty.

He also likes to "reuse" his clothes, including underwear and socks.

I have gifted him personal hygiene products for every Christmas and birthday and have explicitly told him I can smell him and it's not a pleasant one.

I have been leaving all the windows in the flat open for 30 mins every morning for fresh air.

I'm trying to leave the flat, but flat hunting hasn't been going well.

How many days is the longest interval for showers in your opinion? What else could I do to get out of this sensory hell?

Edit - Thank you everyone for the comments. I feel less judgemental now.