I’ve been super-happy with the tank life.of the Form 4 tanks, especially with the Form 3 tanks not ever having a spectacular longevity. I’ve got one tank Formlabs sent me ages ago for beta testing with around 170K layers and still printing perfectly. I have had only one failure, on a not-so-old tank, but it was because a failed print damaged the film. I printed around the bad spot for the remaining prints in the production run, but did need to replace it after that.