How many times can pleural effusion be drained without coming back?

Depends: Mainly on why you got it. An effusion from cancer or heart failure isn't going to go away permanently.

No limit: Generally, no limit on "how many times". However, the more times someone undergoes an invasive procedure the greater risk of complications. Key to preventing recurrence is answering "why did you get the effusion?". Then treat the primary cause. Be well.