That’s a good question. I’ve wondered that myself.
I generally use my cannulas for about 6 months at a time, at which time they get stiff and uncomfortable, so I get a new set.
I’ve NEVER changed my bubbler hoses (since 2005) and there is no observable ‘bacteria’ or mold in them…
And my home is in a high humidity area (next to a large lake) so I get mold in my toilet, etc.
But the electrolyzer gas hoses stay nice and clean inside.
Do you clean the tubes, and if so, how, and how often?