I have the one game plan, so I usually get one game per week, I mainly use this site to get games I just want to play the storyline of and not online or 100 hour gameplays. If I get a game on mon or tues I can be done with it hopefully by thurs or fri, send it back and get the next one mon or tues.
It depends on a lot of things, right now there are a lot of people asking why is it taking so long and such... be sure to take into account the delays, and other randoms that pop up like no mail on sundays, a boom in mail shipment due to holidays or events, and of course the weather....
but for me it usually takes 3 or 4 days. getting on a good schedule with the games made it seem really fast for me.