Welcome to our forum.
I've never shopped around, just go to my dealer but I've heard that Hot Springs owners have to take out a second mortgage when they have to replace theirs.
The new Tri-X are supposed to take care of that for the HS owners. We've been shopping and all of the dealers are willing to throw the Tri-X in on the spas that don't come with them since you can just throw them in the dishwasher. Depending on the salesperson, I've been told 'lifetime' and 7-10 years. Maybe an HS owner (or dealer)could chime in about their experience with them. I'm curious since there appear to be no 'aftermarket' outlets for HS filters (at least that I can find....).The Doob