Ideally you should get periodic bloodwork all through your cycle, at the end, AND afterwards. Getting it done immediately at the end lets you know what you need to watch for improvements, and is useful for future cycles. After that it kind of depends on what you’re looking for and what you were taking. Every 4 weeks is a decent amount of time to wait imo. A lot of doctors don’t test more often than that for monitoring purposes outside of a hospital setting.