Never. I really don't get why people get so grossed out by this, if it really is about discharge does it actually make a huge difference whether it is in my underwear or my yoga pants? Also on the sweat factor if I work out hard enough crotch sweat would go through the underwear anyway- I personally find it more comfortable, I have tried it both ways and nothing horrible or disgusting has ever happened!
+1
And to PP who asked, yes I have children.. but what in the world does that have to do with this topic? If you stink down there, it's not bc you've had kids...maybe try drinking more water?