I'll just say this ....
IMO - if you are a beginner - have little experience with salt tanks - I would recommend starting off with some level of water change once a month minimum.
As you learn and become more experienced with YOUR unique individual tank - with it's unique filtration setup - bioload - freshwater source -and your own personal maintenance routine/test results - you may find it unnecceassry to do water changes as often. Look to your fish and inverts. They will let you know if something is wrong. You'll know it, hopefully not too late though.
Many experienced hobbyists don't do water changes at all and their tanks do great.
Although .... IN MY OPINION
I'm a firm believer that eventually - some form of water exchange will be required. We don't test every known or unknown compound that accumulates in our tanks. Ain't no way Jose'. Exchanging fresh saltwater for old is IMO the only way to reduce any possible build up of unknown toxins that may accumulate.
Do you know if saltwater dissolves plastics, pvc, acrylic or vinyl ?
Do we test for all heavy metals ?
Do we test for hydrocarbons, organic wastes, total organic carbon ?
Skimmers can remove some of these compounds - but if you are going skimmerless -
Just a thought -