It’s almost impossible to track how often Redd visits your island in New Horizons. When the game initially came out, and Redd was introduced, players would go months without him visiting. It was frustrating for anyone trying desperately to bulk out their art collection, but as the game has received several more patches, it seems that Redd will visit a player's island once every two weeks. Additionally, he resides on Harv’s island following the 2.0 update, where he sells two pieces of art a day. Visiting Redd’s island is a much more reliable way to buy art than waiting for the Treasure Trawler to dock!