The safety net is actually ten hours and it starts kicking in at six hours by slowly ramping up your drop rate until it reaches 100% at ten hours. They said their goal with the base drop rate was for people to go no more than two hours without a legendary is all.
As for the event, I wouldn't be surprised if they increased drop rates for the anniversary. Here's to wishin' everyone good luck whether DB is going (probably will be) or not!