the fuel drain orings leak do not leak because of USLD. they leaked before that fuel went to market. be careful what you hear and what you believe.
X2.
They begin to leak.. because they, like many seals & gaskets, simply dry up with age.. and loose their integrity and resilience.
Opening & Closing (exorcising) the drain valve a couple'a times.. Like during a filter change (?) Is a Good thing. IMO