How often to call DQN Replay memory?

I am noob to Machine Learning. I am running a DQN code, I understand the concept of Replay Memory but I don’t understand how often shoud it be run. I saw one code calling it once in every ‘episode’ and in another code it was called every iteration in each episode.

Obviously, calling it more often consumes lots of time, and not calling it more often would probably affect the performance of learning agent. So, my question is should I call it once evry episode or should I call it ‘t’ times in each episode?

Many thanks!