IF I do an IFR flight using the FSX ATC, then I create my first waypoint about 40 miles from my departure airport. I place my last waypoint, before my arrival airport, at about 70-80 miles away.
The reason for that last waypoint being more than 70 miles away is because the FSX ATC always starts to vector me from about 70 miles from the destination. I cannot remember it ever vectoring me to the destination at a greater distance than that. In GA aircraft, I have received the vectoring at as low as 30 miles (this happened the other day).