At least in the astropy versions current while this was written, when the client object just vanished, it would not tell the hub it was dead, and hence zombie clients would slowly aggregate, for instance in TOPCAT’s SAMP client line. Even if astropy were to get a bit smarter here, objects are in a precarious state when the automatic garbage collection strikes. Doing explicit connection management therefore is highly preferable in any case. In particular if it’s as simple as just using a context manager.