I've had my ZZ plant (Zamioculcas zamiifolia) for about eight months now and I'm still amazed at how little it needs

I've had my ZZ plant (Zamioculcas zamiifolia) for about eight months now and I'm still amazed at how little it needs. I water maybe once every three weeks in my tropical humidity, and it just keeps putting out these glossy new leaflets. My one question though—is it normal that the stems are kind of soft near the soil? I'm worried I might be overwatering despite the infrequent schedule. Any tips from folks with more experience?