What are reasonable levels for the ERLE (Echo Return Loss Enhancement) in acoustic echo cancellation?
It is annoying that I replied after 4 years, but this is helpful to others

Yes, ERLE has to be minimum of 40 dB for good echo cancellation. During the presence of only near end speech, you should not calculate ERLE as it will be near to 0dB, so ERLE has to be used only in presence of Far_end signal.

In your case I think you might be using low average filter length for calculation of ERLE. It mainly depends how you are calculating ERLE, ideally if you have ERLE 100 dB after convergence of your adaptive filter, then it is good enough.

Regards