Same here, 1%. However, 1% on some fleet groups (767, A330 at 2:10) is far more reasonable than others (757 at 1:55), but as Sami said it also depends on the mission the plane just flew. An A330 that just flew from JNB to LHR will, understandably, need far more time to prep for the next flight than an A330 that just flew LHR-AMS.
In my scheduling, I have noticed that there is a small decrease in on time percentage from 1% chance to ~8% chance, much smaller than the 7% decrease expected, so I normally feel comfortable going to 8% or so, but not much past that. But, I do still try for 1% chance of delay because until now, I thought there was much more benefit to that number than it seems there really is.