I replaced one after a little over a year. It wasn't defective or discoloured, but it didn't hold up as well, I guess the elasticity just wore off a bit. I still have it as a spare for emergencies, but bought a new one. Basically, I think you can use it for several years without any problems as long as it is not defective.

Hey vellonee, basically you don't have to replace the menstrual cup unless it's defective or the discolouration bothers you. When I empty the cup, I wash it thoroughly before putting it back in. At the end of the period, I sterilise it in boiling water for 10 minutes. Both my cups have not discoloured. I am very satisfied 😀