Struggling to hear quantity length differences in rapid speech

I record my own Estonian pronunciation daily to improve, but I find that my ears struggle to distinguish between the three degrees of quantity (short, long, and overlong) when natives talk at full speed. I feel like 'k' vs 'kk' vs 'kkk' sounds identical in certain contexts, which makes my own reproduction sound robotic. Is there a specific technique for training my ears to catch these nuances, or is it purely a matter of exposure?