Probably once a week initially for the first month. Then once a fortnight thereafter. Why? It’s like anything you’ve learnt. If you don’t practice regularly, you’ll forget it, not the best idea when you’re flying a plane.
It’s important to note though, with more experience you don’t need to practice as regularly to stay proficient. This really highlights that gaining your certificate or licence in the shortest possible time frame is the most efficient and economical way to do it.