I don't test as often as I used to, and should probably do more, with the exception of salinity, my refractometer sits on the kitchen counter since I use it so much. Once I figured out that my salt replaces enough calcium when I do water changes I stopped testing it as often, now that's usually about once a month or so. Same with nitrate, once it got to 0, and I realized that my water changes keeps it in check, I stopped testing so often. The other usual suspects have been in check, with the occasional fluctuation. When cycling a new tank, though, I test that daily for the full spectrum.