I think doing things when needed is probably the best option. But that works if you have a newer house or recently replaced plumbing. There are a lot of really old houses where the pipes and drainage systems are seriously worn out, and in those cases it’s better to talk to a good plumber. A plumber from bens plumbing https://bens.plumbing/areas/kirkland/drain-cleaning/ told me that for my situation, one preventive inspection once a year would be enough.