... Normally, because of leaking, I clear my mask numerous times during a dive. It seems like it is generally after clearing it a few times that I start getting fogging.
That's pretty much why I gave up and joined the Sea Drops herd: that stuff tends to stay on longer than any diluted-baby-dish-poo recipes. If mask leaks, if comes off when I jump off the boat, etc., etc., it'll usually last me till the end of the dive anyway.