I know people that change their socks less often than once a week. And they have never had an issue with athletes foot, fungal infections, bacterial issues etc.
Original poster: change your socks us often or as unoften as you want. It's your feet, your socks. Do what's best for you. And don't spare a 2nd thought as to what other people do. They can do as they wish and you can do as you wish.
The frequency of you changing your socks is totally unimportant from a health point of view - when compared to what you eat and drink.
You'll probably find that many of the people that are quick to judge you or criticise you for changing your socks once every 3 or 4 days are the sort of people that have diets that are far more damaging to their health than if they changed their socks once per year.
But that's human nature. To make decisions on the basis of emotions or inertia. Instead of pure logic.
As well as it being human nature to try take the splinter out of one's neighbour's eye whilst having a plank in one's own.