My safe time, tested using red LEDs, Rubylith, and the method described by Matt (which is the only meaningful test method for paper fogging), exceeds 60 minutes when using Ilford MGIV RC. I stopped the test as being pointless beyond that.
If you are only getting 3-7 minutes safe, then your red LEDs are also emitting tiny bits of blue and/or green light. Most do. You can't see it with the naked eye. Check by reflecting your LEDs off the surface of a common CD. It acts like a prism.
[Edit: I see you did mention using Rubylith. Did it completely cover the globe? I'm using a strip of six 1-watt red 635nm LEDs. They sit atop a Thomas Duplex suspended from the ceiling. It's a smallish darkroom, only about 8x11-feet. My LEDs are light-tight under the Rubylith.]