Rule of thumb is a strong hive will fill a 10fr deep super in 10-12 days on Canola, which then gets pulled off and replaced. That’s usually an ok time to go without worrying about candying. Any longer and you will have problems. You should be able to tap the hive fairly frequently to avoid it. I only run conventional hives though so I am not sure how flow frames will hold up. If the aim is to build the colony, take the super off until the box is full of bees, then put it back on and consider running regular frames that you can later use as a backup food source for the bees in dry times.