The timings are really unpredictable. It's not always the same. It depends on how the server/realm runs, your internet connection and such.
An example on my end:
- Midnight is usually hard for me to dupe, there are times that the duping process is good, there are times that it's not.
- I have the best duping experience during a few hrs after noon.
- morning, not sure.
So far, from my experience on duping, I could check and see what timings I need to dupe successfully by looking at how connecting and connected moves. If it goes fast/normal (just as long as the wait in between trying to reconnect again is like 2-3 seconds), I can dupe good enough.
- with this kind, my timing is at the end of connected message.
If the interval in between connecting and connected is wide, it'd be doing some sniffing to get the timing out of it.
- it's usually just before connected.
You'd know when you duped successfully. It's when the other client connects fast before the red message appears.