Can you let me know how many times can pleural effusion be drained?

Many: But better to get it fully drained once, and the cause identified and treated to prevent the recurrence. Some cannot be stopped, but can be internally drained with devices.

As many as..., but..: Draining effusion is a part of symptomatic care, which may be done as many/often as clinically needed, but comes with increasing complications such as infection, pain, etc. due to its often related-with chronically debilitating illnesses in attesting life is a one-way street of accumulation, modification, & continuation. So, ask more concerns or issues with the treating doctors.