I generally do twice a year too. I like turbos, trochus and cerith snails. I have a few hermits, but have had some bad experiences with them so I only have 20 or so in a 210 gallon.
I have a nano tank and I really found myself neglecting replenishing mine. I tend to think more about coral than crabs and snails that seem to knock stuff over or get in the way mostly. I recently noticed that things were dwindling and picked up a few snails and hermits at Nemo Aquarium in Duluth. Although I wasn’t considering that my fire shrimp and pom pom/boxing crab are also part of the CUC. I think of them as ornamental but they do serve a purpose I guess