[gascan]

washing it as soon as possible after sessions

That's just good practice in general, the salt & sweat come out easier when they haven't fully dried yet, and the bacteria won't have as much time to grow their numbers and make the garment permanently smelly.

[Noumenon72]

I am anosmic who does laundry every 3 weeks. How much time does it normally take to become permanently smelly? Do you have to be drenched in sweat? Will the smell transfer to other clothes in the basket?

[gascan]

1) depends massively on the fabric

2) also depends on the fabric, but usually you have to be pretty sweaty, at least to the wet-armpits level. Just think of the level where you will be depositing salt on the clothes.

3) Not often.

If you don't want to do laundry right away, you can soak the salty clothes, squeeze them dry, and hang them.

[sdhgaiojfsa]

Nobody knows the answer to these questions, and I'd question anyone who represents that they do. "Some time." "Maybe." "Somewhat, perhaps."

It would probably be wise for you to increase your washing frequency, nevertheless.