I doubt any of us really underestimates how busy it can be for ATC at times but leaving somebody 4 minutes on 'standby' seems a bit long, especially on an apparent handover. I'm sure I'd start to think I'd been forgotten after a couple of minutes which can seem a long time in the air on a frequency that appears quiet.
There is an added flight safety risk with the stress level of being left hanging without a clearance to enter and approaching controlled airspace. As others have said better to have a plan B already worked out in your head.
Better again would be something along the excellent response I had when approaching Lakenheath recently when after the standard initial call the response was 'G-*** clear to enter Lakenheath MATZ, standby'