I haven't really experimented enough to verify to myself that the following is true so I am relying on what Ansel Adams and Polaroid have written in years past to be true. In general, overdeveloping does not occur or, if it does, it is a slight amount. This is because the chemical reactions taking place are structured so that they play out after a little over a minute or so.
In my own verification, I always develop Type 55 negatives for a full minute, contrary to the instructions. Nothing really changes going even a bit longer.
I have intentionally tried this with Fuji and your mileage may vary. But I kind of doubt any real harm will come from overdeveloping.