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If I'm not mistaken they last about 10 years or at least 5. Mine are probably 2.5 or so... not exactly sure how long they were in use before I got the tub but it was minimal. Now, I must say i have six filters... 5 are the same and one is slightly different. It is this different one that cracked. This different one has one has warn much differently than the others. Not sure what the dealio with that is. But it is like pealing on the top and looks nasty and weird where as the others all look brand new. Maybe i somehow got a factory reject, lol. Someday I'll take a pic and share.
I'm sure I probably should replace it and eventually I will, but with J being on dissability right now... and money at a premium a $70 filter isn't gonna happen. I'll put on my one spare for the time being.