How much impression is good for testing?

I’m talking about Facebook PPC right now, let say If my ad is running 4k imps with a ctr 0.02 should I ditch it and move on with other well performing ads? or should I wait a while for more impression see if the CTR increase or not?
Currently my highest CTR ad is 0.057% don’t know if I should tweak it or just start making some new ads. Any suggestions?

See original post by pk7677