Hi @Reine,
You can find some suggestions from other users in this thread: Build Tank Low Health Warning. The most practical option would be to plan out the prints you need to run so that they can be done within the tank’s lifetime, although I can understand how this might be tricky depending on your print schedule. Aside from that, you can pour the resin out of the tank into a separate container in between uses. This won’t extend the tracked lifetime of the tank, but it certainly wouldn’t hurt to do.